阅读说明：本技术 一种倍半稀土硫化物高熵陶瓷材料及其制备方法和应用 (High-entropy sesqui-rare earth sulfide ceramic material and preparation method and application thereof ) 是由 陈玉奇 于 2021-09-28 设计创作，主要内容包括：本发明提供一种倍半稀土硫化物高熵陶瓷材料及其制备方法和应用,倍半稀土硫化物高熵陶瓷材料的化学式为(Ln～(1)-(y1)Ln～(2)-(y2)Ln～(3)-(y3)Ln～(4)-(y4)Ln～(5)-(y5))S-(x)；稀土元素Ln～(i)-(yi)为Sc、Y、La、Ce、Pr、Nd、Sm、Gd、Tb、Dy、Ho、Er、Tm、Yb和Lμ中的4种以上；其中,y1+y2+y3+y4+y5＝1,1.33≤x≤1.5；倍半稀土硫化物高熵陶瓷材料的制备方法包括：称料,混料,煅烧,硫化,热处理,烧结成型的步骤。本发明制备的高纯倍半稀土金属硫化物单相高熵陶瓷粉体纯度高,制备简单,能够批量化生产,适用于颜料和填料等改色剂,色彩丰富且无毒；适用于高温热电功能陶瓷材料,结构稳定性能好。(The invention provides a sesqui-rare earth sulfide high-entropy ceramic material and a preparation method and application thereof, wherein the chemical formula of the sesqui-rare earth sulfide high-entropy ceramic material is (Ln) 1 y1 Ln 2 y2 Ln 3 y3 Ln 4 y4 Ln 5 y5 )S x (ii) a Rare earth element Ln i yi 4 kinds of Sc, Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and L muThe above step (1); wherein y1+ y2+ y3+ y4+ y5 is 1, and x is more than or equal to 1.33 and less than or equal to 1.5; the preparation method of the high-entropy sesqui-rare earth sulfide ceramic material comprises the following steps: weighing, mixing, calcining, vulcanizing, performing heat treatment, and sintering and molding. The high-purity sesqui rare earth metal sulfide single-phase high-entropy ceramic powder prepared by the method has high purity, is simple to prepare, can be produced in batch, is suitable for color modifiers such as pigments and fillers, and is rich in color and nontoxic; is suitable for high-temperature thermoelectric functional ceramic materials and has good structural stability.)

1. The high-entropy sesqui-rare earth sulfide ceramic material is characterized by having a chemical formula of (Ln)¹ _y1Ln² _y2…Lnⁱ _yi)S_x，Lnⁱ _yiMore than 4 of Sc, Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and L mu; wherein y1+ y2 … + yi is 1, and x is more than or equal to 1.33 and less than or equal to 1.5.

2. The high entropy rare earth sesquisulfide ceramic material of claim 1, wherein Lnⁱ _yi5 types of Sc, Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and L mu; wherein y1+ y2+ y3+ y4+ y5 is 1, and x is more than or equal to 1.33 and less than or equal to 1.5;

preferably, x is 1.5.

3. Sesqui-rare earth sulfide high-entropy ceramic material as claimed in claim 1 or 2, wherein the raw material of rare earth element Ln is rare earth oxide or rare earth salt;

preferably, the rare earth salt is any one of rare earth nitrate, rare earth chloride, rare earth sulfate, rare earth carbonate and rare earth oxalate.

4. A high entropy rare earth sesquisulphide ceramic material according to claim 3, wherein the rare earth oxide has a particle size not greater than 10 μm and a specific surface area greater than 5m²/g。

5. A method for preparing a high-entropy sesqui-rare-earth sulfide ceramic material according to any one of claims 1 to 4, comprising the steps of:

step 1, weighing materials, namely weighing raw materials containing different types of rare earth elements according to a ratio to form a rare earth mixed raw material;

step 2, mixing materials, adding the rare earth mixed raw material and a first solvent into a ball mill for ball milling treatment when the rare earth element raw material is rare earth oxide, rare earth carbonate or rare earth oxalate to obtain mixed material slurry, and heating and sieving the mixed material slurry to obtain an initial vulcanization precursor;

when the rare earth element raw material is rare earth nitrate, rare earth chloride or rare earth sulfate, mixing the rare earth mixed raw material with a second solvent, heating and stirring to obtain a multi-element rare earth gel;

step 3, calcining, namely drying and calcining the multicomponent rare earth gel, cooling to room temperature, taking out, grinding and sieving to obtain a multicomponent rare earth sulfide precursor;

step 4, performing vulcanization treatment, namely putting the initial vulcanization precursor or the multi-component rare earth vulcanization precursor into a quartz crucible, putting the quartz crucible into an inert gas protection or vacuum tube furnace for vulcanization treatment, introducing sulfur-containing mixed gas with the flow of 30-300 mL/min, heating to 700-1200 ℃, preserving heat for 1-100 h, grinding and sieving to obtain high-entropy ceramic powder containing the sesqui-rare earth sulfide;

and 5, performing vacuum heat treatment, namely placing the high-entropy ceramic powder containing the sesquialter rare earth sulfide in an atmosphere tube furnace, performing heat treatment in a vacuum state, cooling to room temperature, and taking out to obtain the high-purity sesquialter rare earth sulfide high-entropy ceramic powder.

6. The method for preparing a high entropy sesqui-rare earth sulfide ceramic material as claimed in claim 5, wherein the method further comprises step 6, sintering and forming;

and placing the high-purity sesqui-rare earth sulfide high-entropy ceramic powder into a mold, performing cold press molding, then placing into a sintering furnace for pressure sintering, and performing heating and pressure sintering under the protection of inert gas or in a vacuum state to obtain the rare earth sulfide high-entropy ceramic block.

Preferably, the high-purity sesqui-rare earth sulfide high-entropy ceramic powder is placed in a graphite mold, prepressing forming is carried out firstly, then the formed block is placed in a hot pressing furnace or a discharge plasma sintering furnace for sintering forming, the loading pressure of the hot pressing furnace is 30-50 MPa, the load of the surface of a sample of the discharge plasma sintering furnace is 50-80 MPa, the sintering temperature is 1000-1550 ℃, the heating rate is 10-50K/min, the heat preservation time is 30-600 min, and the cooling rate above 800 ℃ is not more than 25K/min;

preferably, the high-purity sesqui-rare earth sulfide high-entropy ceramic powder is cold-pressed and molded in a stainless steel mold or a hard alloy mold, the pressure is 35-50MPa, the pressure is maintained for 1-5min, the block after cold-pressing molding is placed in a furnace with a pressurizable atmosphere for sintering, the sintering temperature is 1300-1550 ℃, the heating rate is 10-25K/min, the heat preservation time is 20-120 min, the pressure of pressure-maintained gas is 5-15 MPa, and the cooling rate above 800 ℃ is not more than 15K/min.

7. The method for preparing the sesqui-rare-earth sulfide high-entropy ceramic material as claimed in claim 5, wherein in the step 1, five different kinds of rare-earth element raw materials are weighed according to the mixture ratio, and the molar ratio of the five kinds of rare-earth element raw materials is 1:1:1: 1;

preferably, the first solvent is an inorganic solvent, an organic solvent or an inorganic-organic mixed solvent; the second solvent is a mixture of citric acid, glycol and distilled water;

still preferably, the rare earth mixed raw material, citric acid, ethylene glycol and distilled water satisfy a molar ratio of 1: (0.5-12): (12-40): (8-15).

8. The method for preparing the high-entropy sesqui-rare-earth sulfide ceramic material as claimed in claim 5, wherein in the step 2, the heating and stirring after mixing the rare-earth mixed raw material and the second solvent are specifically as follows: uniformly mixing the rare earth mixed raw material and a second solvent, setting the heating temperature to be 70-100 ℃, stirring for 30-120 min, then heating to 150-250 ℃, and continuously stirring for 30-120 min to obtain the multicomponent rare earth gel;

preferably, in the step 3, the specific process of calcining is as follows: heating to 300-380 ℃, and preserving heat for 60-220 min; continuously heating to 350-675 ℃, and preserving heat for 6-48 h;

preferably, in the step 4, the sulfur-containing mixed gas is a mixed gas of carbon disulfide and argon, the flow rate of the sulfur-containing mixed gas is 50-100 mL/min, the vulcanization temperature is 800-1000 ℃, and the heat preservation time is 1-12 h.

9. The method for preparing the sesqui-rare earth sulfide high-entropy ceramic material as set forth in any one of claims 5 to 8, wherein in the step 5, the specific process of the heat treatment is as follows: vacuum-pumping to 0.6X 10^-1～7×10^-3Pa, heating to 1000-1550 ℃ in a vacuum state, and keeping the temperature for 3-24 h.

10. The application of the high-entropy sesqui-rare-earth sulfide ceramic material prepared by the preparation method of the high-entropy sesqui-rare-earth sulfide ceramic material as claimed in any one of claims 5 to 9, wherein the high-entropy sesqui-rare-earth sulfide ceramic material is applied to a high-temperature thermoelectric functional ceramic material.

Technical Field

The invention belongs to the technical field of functional ceramic material preparation, and particularly relates to a high-entropy sesqui-rare earth sulfide ceramic material and a preparation method and application thereof.

Background

The traditional material design is to dope specific elements or compound special functional molecules with single or double-component main components to improve the comprehensive performance. With the progress of science and technology, increasingly complex and harsh working conditions put higher requirements on the comprehensive use performance of materials. In order to develop a novel ceramic material used under extreme conditions, the high-entropy ceramic exhibits excellent overall properties by virtue of a high-entropy effect, a delayed diffusion effect, a lattice distortion effect and a cocktail effect.

The high-entropy ceramic generally refers to a ceramic material with a simple crystal structure, which is composed of four or more metal elements and one non-metal element, and the common ceramic material is a five-membered crystal structure, which is composed of five metal elements and one non-metal element. The discovery of (mgnico μ Zn) O in 2015 extended the concept of high entropy from alloys to ceramic materials for the first time. The high-entropy ceramics mainly comprise oxides (MgNiCouZn) O and the like, transition metal sulfides (Cmu)₅SnMgGeZn)S₉Etc. boride (Ti)_0.2Zr_0.2Nb_0.2Hf_0.2Ta_0.2)B₂Etc., carbides (Ti)_0.25V_0.25Zr_0.25Nb_0.25) C, nitride (ZrVNbCrMo) N and silicide (Ti)_0.2Zr_0.2Nb_0.2Mo_0.2W_0.2)Si₂And the like.

In the prior art, high-entropy ceramics are divided into oxide high-entropy ceramics, boride high-entropy ceramics, carbide high-entropy ceramics and nitride high-entropy ceramics according to anion compositions. Various high-entropy ceramics are comprehensively optimized based on the performance of binary parent compounds. Oxide high-entropy ceramics, boride high-entropy ceramics, carbide high-entropy ceramics and nitride high-entropy ceramics can not meet the use requirements of thermoelectric materials and other fields in the field of functional ceramics, particularly electrical properties and thermal properties. The strong covalent bond between the metal cation and the anion is not favorable for the formation and transfer of electrons or holes, thereby being not favorable for the regulation and control of electron and phonon transport.

Therefore, there is a need to provide an improved solution to the above-mentioned deficiencies of the prior art.

Disclosure of Invention

The invention aims to provide a sesqui-rare earth sulfide high-entropy ceramic material and a preparation method and application thereof, and aims to solve the problems that the conventional multi-component sulfide high-entropy ceramic material is not ideal in regulating and controlling effects of electrical properties and thermal properties, and the multi-component sulfide high-entropy ceramic material is high in residual oxygen content and carbon content and low in purity.

In order to achieve the above purpose, the invention provides the following technical scheme:

a high-entropy sesqui-rare-earth sulfide ceramic material with a chemical formula of (Ln)¹ _y1Ln² _y2…Lnⁱ _yi)S_x，Lnⁱ _yiMore than 4 of Sc, Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and L mu; wherein y1+ y2 … + yi is 1, and x is more than or equal to 1.33 and less than or equal to 1.5.

In the high entropy ceramic material of the above sesqui-rare earth sulfide, preferably, Lnⁱ _yi5 types of Sc, Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and L mu; wherein y1+ y2+ y3+ y4+ y5 is 1, and x is more than or equal to 1.33 and less than or equal to 1.5;

preferably, x is 1.5.

In the sesqui-rare earth sulfide high-entropy ceramic material, preferably, the raw material of the rare earth element Ln is rare earth oxide or rare earth salt;

preferably, the rare earth salt is any one of rare earth nitrate, rare earth chloride, rare earth sulfate, rare earth carbonate and rare earth oxalate.

In the high-entropy sesqui-rare earth sulfide ceramic material, preferably, the particle size of the rare earth oxide is not more than 10 μm, and the specific surface area is more than 5m²/g。

In the preparation method of the high-entropy ceramic material of the sesqui-rare earth sulfide, preferably, the preparation method comprises the following steps:

step 1, weighing materials, namely weighing different types of rare earth element raw materials according to a ratio to form a rare earth mixed raw material;

step 2, mixing materials, adding the rare earth mixed raw materials and a first solvent into a ball mill for ball milling treatment when the rare earth element raw materials are rare earth oxides, rare earth carbonates or rare earth oxalates to obtain mixed material slurry, and heating and sieving the mixed material slurry to obtain an initial vulcanization precursor;

when the rare earth element raw material is rare earth nitrate, rare earth chloride or rare earth sulfate, mixing the rare earth mixed raw material with a second solvent, heating and stirring to obtain a multi-element rare earth gel;

step 3, calcining, namely drying and calcining the multicomponent rare earth gel, cooling to room temperature, taking out, grinding and sieving to obtain a multicomponent rare earth sulfide precursor;

step 4, performing vulcanization treatment, namely putting the initial vulcanization precursor or the multi-component rare earth vulcanization precursor into a quartz crucible, putting the quartz crucible into an inert gas protection or vacuum tube furnace for vulcanization treatment, introducing sulfur-containing mixed gas with the flow of 30-300 mL/min, heating to 700-1200 ℃, preserving heat for 1-100 h, grinding and sieving to obtain high-entropy ceramic powder containing the impurity sesqui-rare earth sulfide;

and 5, performing vacuum heat treatment, namely placing the high-entropy ceramic powder containing the sesquialter rare earth sulfide in an atmosphere tube furnace, performing heat treatment in a vacuum state, cooling to room temperature, and taking out to obtain the high-purity sesquialter rare earth sulfide high-entropy ceramic powder.

The preparation method of the high-entropy sesqui-rare earth sulfide ceramic material preferably further comprises the step 6 of sintering and forming;

placing high-purity sesqui-rare earth sulfide high-entropy ceramic powder into a mold, performing cold press molding, then placing into a sintering furnace for hot-press sintering, and performing heating and pressure sintering under the protection of inert gas or in a vacuum state to obtain a rare earth sulfide high-entropy ceramic block;

preferably, high-purity sesqui-rare earth sulfide high-entropy ceramic powder is placed in a graphite mold, pre-pressing molding is carried out firstly, then a molded block is placed in a hot pressing furnace or a discharge plasma sintering furnace for sintering molding, the loading pressure of the hot pressing furnace is 30-50 MPa, the load of the surface of a sample of the discharge plasma sintering furnace is 50-80 MPa, the sintering temperature is 1000-1550 ℃, the heating rate is 10-50K/min, the heat preservation time is 30-600 min, and the cooling rate above 800 ℃ is not more than 25K/min;

preferably, the high-purity sesqui-rare earth sulfide high-entropy ceramic powder is cold-pressed and molded in a stainless steel mold or a hard alloy mold, the pressure is 35MPa-50MPa, the pressure is maintained for 1-5min, the block after cold-pressing molding is placed in a furnace with a pressurizable atmosphere for sintering, the sintering temperature is 1300-1550 ℃, the heating rate is 10-25K/min, the heat preservation time is 20-120 min, the pressure of pressure-maintained gas is 5-15 MPa, and the cooling rate above 800 ℃ is not more than 15K/min.

In the preparation method of the sesqui-rare earth sulfide high-entropy ceramic material, preferably, in step 1, five different kinds of rare earth element raw materials are weighed according to the mixture ratio, and the molar ratio of the five kinds of rare earth element raw materials is 1:1:1: 1;

preferably, the first solvent is an inorganic solvent, an organic solvent or an inorganic-organic mixed solvent; the second solvent is a mixture of citric acid, glycol and distilled water;

still preferably, the rare earth mixed raw material, citric acid, ethylene glycol and distilled water satisfy a molar ratio of 1: (0.5-12): (12-40): (8-15).

In the above method for preparing the high-entropy sesqui-rare-earth sulfide ceramic material, preferably, in step 2, the steps of mixing the rare-earth mixed raw material with the second solvent, heating and stirring are specifically as follows: uniformly mixing the rare earth mixed raw material and a second solvent, setting the heating temperature to be 70-100 ℃, stirring for 30-120 min, then heating to 150-250 ℃, and continuously stirring for 30-120 min to obtain a multi-element rare earth gel;

preferably, in step 3, the specific process of calcination is: heating to 300-380 ℃, and preserving heat for 60-220 min; continuously heating to 350-675 ℃, and preserving heat for 6-48 h;

preferably, in the step 4, the sulfur-containing mixed gas is a mixed gas of carbon disulfide and argon, the flow rate of the sulfur-containing mixed gas is 50-100 mL/min, the vulcanization temperature is 800-1000 ℃, and the heat preservation time is 1-12 h.

In the preparation method of the high-entropy sesqui-rare earth sulfide ceramic material, preferably, in step 5, the specific process of the heat treatment is as follows: vacuum-pumping to 0.6X 10^-1～7×10^-3Pa, heating to 100 deg.C under vacuumThe temperature is 0-1550 ℃, and the heat preservation time is 3-24 h.

The application of the high-entropy sesqui-rare earth sulfide ceramic material prepared by the preparation method of the high-entropy sesqui-rare earth sulfide ceramic material is applied to high-temperature thermoelectric functional ceramic materials.

Has the advantages that:

the electron and hole concentrations of the rare earth metal sulfide high-entropy ceramic material are easy to generate, and the electric heat transport performance is easy to regulate and control; the rare earth metal sulfide has the advantages that the rare earth metal sulfide has the characteristics of lanthanide rare earth cation radius shrinkage and 4f local area, the chemical properties similar to elements are easily generated to be mutually solid-dissolved, and the high-entropy ceramic structure has good stability.

The high-entropy sesqui-rare earth sulfide ceramic also has the following advantages:

1. the in-situ rapid synthesis can be realized, the preparation temperature is low, the single phase can be rapidly synthesized by optimized raw materials at 800-1000 ℃, and the synthesis temperature of the carbide high-entropy ceramic and boride high-entropy ceramic solid-phase method is generally not lower than 1500 ℃; the high-entropy ceramic powder of the sesqui-rare earth sulfide has high purity;

2. the method has simple preparation process, the single-time yield of the prepared powder can reach about 100g, the method can be used for mass production, and the high-entropy sesqui-rare earth sulfide ceramic powder is suitable for color modifiers such as pigments and fillers, and has rich colors and no toxicity;

3. the final product has good performance, is suitable for high-temperature thermoelectric functional ceramic materials, has good structural stability, and improves a high-temperature electrothermal transport mechanism.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. Wherein:

FIG. 1 shows an embodiment of the present inventionSingle-phase sesqui-rare earth sulfide high-entropy ceramic material (Sc) of example 1_0.4 Y_0.4La_0.4Ce_0.4Pr _0.4)S₃SEM picture of (1);

FIG. 2 is a single-phase sesqui-rare earth sulfide high-entropy ceramic material (Sc) of example 1 of the present invention_0.4 Y_0.4La_0.4Ce_0.4Pr _0.4)S₃SEM-EDX surface scanning element distribution diagram;

FIG. 3 is a single-phase sesqui-rare earth sulfide high-entropy ceramic material (La) of example 2 of the present invention_0.4Ce_0.4Pr_0.4Nd_0.4Sm_0.4)S₃SEM picture of (1);

FIG. 4 is a single-phase sesqui-rare earth sulfide high-entropy ceramic material (La) of example 2 of the present invention_0.4Ce_0.4Pr_0.4Nd_0.4Sm_0.4)S₃SEM-EDX surface scanning element distribution diagram;

FIG. 5 is a single-phase sesqui-rare earth sulfide high-entropy ceramic material (Y) of example 3 of the present invention_0.4La_0.4Ce_0.4Pr_0.4Nd_0.4)S₃SEM picture of (1);

FIG. 6 is a single-phase sesqui-rare earth sulfide high-entropy ceramic material (Y) of example 3 of the present invention_0.4La_0.4Ce_0.4Pr_0.4Nd_0.4)S₃SEM-EDX surface scanning element distribution diagram;

FIG. 7 is a single-phase sesqui-rare earth sulfide high-entropy ceramic material (Y) of example 4 of the present invention_0.4La_0.4Ce_0.4Pr_0.4Sm_0.4)S₃SEM picture of (1);

FIG. 8 is a single-phase sesqui-rare earth sulfide high-entropy ceramic material (Y) of example 4 of the present invention_0.4La_0.4Ce_0.4Pr_0.4Sm_0.4)S₃SEM-EDX surface scanning element distribution diagram;

FIG. 9 is a comparison graph of XRD patterns of direct sulfidation after mixing of two element rare earth oxides according to comparative example 1 of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments that can be derived by one of ordinary skill in the art from the embodiments given herein are intended to be within the scope of the present invention.

The present invention will be described in detail with reference to examples. It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.

The high-entropy sesqui-rare earth sulfide ceramic material and the preparation method thereof provided by the invention can be used for preparing powder or blocks as the ceramic material of functional ceramics. The method comprises the steps of firstly realizing uniform mixing among different rare earth elements through ball milling treatment, then carrying out high-temperature vulcanization treatment on a multi-element rare earth-containing precursor mixture to prepare the high-entropy sesqui-rare earth sulfide-containing ceramic powder, then reducing the impurity content in the high-entropy sesqui-rare earth sulfide ceramic powder by combining vacuum heat treatment while regulating the non-stoichiometric sulfur content, and finally obtaining the high-entropy sesqui-rare earth sulfide ceramic block through pressure sintering and forming.

In addition, the invention can adopt a mode of preparing rare earth sulfide high-entropy ceramics by mixing and sintering rare earth oxides, and can also adopt rare earth nitrate, rare earth chloride or rare earth sulfate as raw materials to be added into the preparation reaction for synthesis, on one hand, the atomic-level solid solution of rare earth cations can be promoted by generating multi-element rare earth gel containing multiple rare earth elements, thereby improving the stability of the high-entropy ceramic material of the sesqui-rare earth sulfide, on the other hand, the gel is calcined and decomposed into the rare earth oxycarbonate, and the method can also reduce the reaction temperature, improve the reaction efficiency, accelerate the reaction speed, save the resource and the energy consumption, meanwhile, rare earth nitrate, rare earth chloride or rare earth sulfate is adopted as a raw material, so that the synthesis and crystal structure of the high-entropy sesqui-rare earth sulfide ceramic are not influenced.

The invention provides a high-entropy sesqui-rare earth sulfide ceramic material which comprises sesqui-rare earth sulfide high-entropy ceramic powder and sesqui-rare earth sulfideThe chemical formula of the high-entropy rare earth sulfide ceramic block and the high-entropy sesqui-rare earth sulfide ceramic material is (Ln)¹ _y1Ln² _y2…Lnⁱ _yi)S_x，Lnⁱ _yiMore than 4 of Sc, Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and L mu; wherein y1+ y2 … + yi is 1, and x is more than or equal to 1.33 and less than or equal to 1.5.

Preferably, Lnⁱ _yi5 types of Sc, Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and L mu; wherein y1+ y2+ y3+ y4+ y5 is 1, and x is more than or equal to 1.33 and less than or equal to 1.5; more preferably, x is 1.5. Namely the high-entropy ceramic material of the sesqui-rare earth sulfide has the general formula (nLn)₂S₃Wherein Ln is rare earth element, and n is 5.

The preparation method of the high-entropy sesqui-rare earth sulfide ceramic material comprises the following steps:

step 1, weighing materials, namely weighing different types of rare earth element raw materials according to a ratio to form a rare earth mixed raw material;

in the specific embodiment of the invention, the raw material of the rare earth element Ln is rare earth oxide or rare earth salt; the rare earth salt is any one of rare earth nitrate, rare earth chloride, rare earth sulfate, rare earth carbonate or rare earth oxalate.

The particle diameter of the rare earth oxide is not more than 10 mu m, and the specific surface area is more than 5m²(ii)/g; preferably, nano-level or micron-level powder particles with the particle size of less than 5 mu m are selected, and the specific surface area of the rare earth oxide particles is 10-50 m²/g。

In the specific embodiment of the invention, five different kinds of rare earth element raw materials are weighed according to the proportion, and the molar ratio of the five kinds of rare earth element raw materials is 1:1:1: 1.

In the specific embodiment of the invention, the high-entropy sesqui-rare earth sulfide ceramic material can be rapidly prepared by adopting the rare earth oxide. The rare earth carbonate and rare earth oxalate can effectively control the appearance of the high-entropy sesqui-rare earth sulfide ceramic. The sesqui-rare earth sulfide high-entropy ceramic fine particles can be obtained by adopting a sol-gel process of rare earth chloride, rare earth nitrate and rare earth sulfate and controlling process parameters, and the solid solubility of rare earth cations is high, so that the sesqui-rare earth sulfide high-entropy ceramic fine particles are good in thermal stability when being applied to functional ceramics.

Step 2, mixing materials, adding the rare earth mixed raw materials and a first solvent into a ball mill for ball milling treatment when the rare earth element raw materials are rare earth oxides, rare earth carbonates or rare earth oxalates to obtain mixed material slurry, heating the mixed material slurry, slowly stirring until the first solvent is completely volatilized to obtain a solid mixed material, and then sieving the solid mixed material to obtain an initial vulcanization precursor;

when the rare earth element raw material is rare earth nitrate, rare earth chloride or rare earth sulfate, mixing the rare earth mixed raw material with a second solvent, stirring and mixing the mixture by constant temperature magnetic stirring, setting the heating temperature to be 70-100 ℃ (preferably 80-100 ℃, such as 85 ℃, 90 ℃, 95 ℃ and 100 ℃), stirring for 30-120 min (such as 40min, 60min, 80min, 100min and 110min), then heating to be 150-250 ℃ (preferably 180-200 ℃, such as 190 ℃, 195 ℃ and 198 ℃), and continuously stirring for 30-120 min (such as 40min, 60min, 80min, 100min and 110min) to obtain the multicomponent rare earth gel.

In the specific embodiment of the invention, in the ball milling treatment in the material mixing process, the grinding ball is one of stainless steel ball, zirconium dioxide ball, tungsten steel ball and agate ball, the diameter of the grinding ball is 5-22 mm, the ball-to-material ratio is (5-20): 1 (such as 6:1, 7:1, 8:1, 9:1, 10:1, 12:1, 14:1, 16:1 and 18:1), and the ball milling speed is 50-600 r/min (such as 80r/min, 100r/min, 200r/min, 300r/min, 400r/min and 500 r/min); the mixing time is 6-72 h (such as 10h, 20h, 30h, 40h, 50h, 60h and 70 h).

Preferably, the first solvent is an inorganic solvent, an organic solvent or an inorganic-organic mixed solvent; in the ball milling process, absolute ethyl alcohol is adopted as the wet milling of the organic solvent.

The second solvent is a mixture of citric acid, glycol and distilled water; still preferably, the rare earth mixed raw material, citric acid, ethylene glycol and distilled water satisfy a molar ratio of 1: (0.5-12): (12-40): (8-15) (e.g., 1:0.5:12:8, 1:1:20:10, 1:12:40: 15).

Step 3, calcining, namely placing the multicomponent rare earth gel into a corundum crucible, placing the corundum crucible into a muffle furnace for drying and calcining, heating to 300-380 ℃ (such as 310 ℃, 320 ℃, 350 ℃, 360 ℃, 370 ℃ and 380 ℃), and keeping the temperature for 60-220 min (70min, 90min, 100min, 150min and 200 min); continuously heating to 350-675 ℃ (such as 400 ℃, 450 ℃, 500 ℃, 550 ℃, 600 ℃ and 650 ℃), and preserving heat for 6-48 h (such as 8h, 10h, 20h, 30h and 40 h); and cooling to room temperature, taking out, grinding and sieving to obtain the multicomponent rare earth sulfide precursor.

Preferably, the calcination temperature of the multicomponent rare earth gel is 400-475 ℃ (such as 420 ℃, 440 ℃, 460 ℃).

Step 4, performing vulcanization treatment, namely placing the initial vulcanization precursor or the multi-element rare earth vulcanization precursor in a quartz crucible, placing the quartz crucible in inert gas protection or a vacuum tube furnace for vulcanization treatment, heating the introduced sulfur-containing mixed gas at the flow rate of 30-300 mL/min (such as 50mL/min, 100mL/min, 150mL/min, 200mL/min and 250mL/min) to 700-1200 ℃ (such as 800 ℃, 1000 ℃ and 1100 ℃) for 1-100 h (such as 2h, 10h, 20h, 50h and 80h), and then grinding and sieving to obtain high-entropy ceramic powder containing the impurity sesqui rare earth sulfide;

more preferably, the sulfur-containing mixed gas is a mixed gas of carbon disulfide and argon, the flow rate of the sulfur-containing mixed gas is 50-100 mL/min (such as 60mL/min and 80mL/min), the vulcanization temperature is 800-1000 ℃ (such as 900 ℃ and 950 ℃), and the heat preservation time is 1-12 h (preferably 2-4 h). Preferably, the temperature of the sulfur-containing mixed gas is 300-800 ℃ (such as 400 ℃, 600 ℃, 700 ℃).

In the specific embodiment of the invention, in the step 4, the front tubular furnace is heated by the sulfurization treatment, and the front tubular furnace is flushed with 0.5-1.5L/min of high-purity argon for 10-60 min (for example, 20min, 40min, 50 min).

Step 5, vacuum heat treatment, namely placing the high-entropy ceramic powder containing the sesquialter rare earth sulfide into a hexagonal boron nitride crucible, putting the hexagonal boron nitride crucible into a high-vacuum atmosphere tube furnace connected with a mechanical pump, a diffusion pump or a molecular pump, preheating a vacuum pump for 15-20 min, and vacuumizing to 0.6 multiplied by 10^-1～7×10^-3Pa, and heating to 1000-1550 deg.C (such as 1100 deg.C and 1200 deg.C) in vacuumAnd at 1300 ℃ and 1400 ℃, carrying out heat treatment for 3-24 h (such as 5h, 10h, 15h and 20h), cooling to room temperature, and taking out to obtain the high-purity sesqui-rare earth sulfide high-entropy ceramic powder. The purity of the high-purity sesqui-rare earth sulfide high-entropy ceramic powder is 99.8-99.9%; the content of impurity carbon and oxygen in the high-entropy ceramic powder of the sesqui-rare earth sulfide can be reduced by heat treatment.

In an embodiment of the present invention, the heat treatment temperature is 1200-1550 ℃ (such as 1300 ℃, 1400 ℃, 1500 ℃).

In the specific embodiment of the invention, in the heat treatment process in the step 5, the hexagonal boron nitride crucible is placed on the reducing graphite plate, and the graphite paper is wrapped around the crucible.

The preparation method of the invention also comprises step 6, sintering and forming; placing high-purity sesqui-rare earth sulfide high-entropy ceramic powder into a mold, performing pre-pressing molding or cold pressing molding, then placing the high-purity sesqui-rare earth sulfide high-entropy ceramic powder into a sintering furnace for hot-pressing sintering, and performing heating and pressure sintering under the protection of inert gas or in a vacuum state to obtain the rare earth sulfide high-entropy ceramic block.

For preparing a regular cylindrical or square rare earth sulfide high-entropy ceramic block, the method comprises the following specific steps: placing high-purity sesqui rare earth sulfide high-entropy ceramic powder into a graphite die, performing prepressing forming on a tablet press at a pressure of 0.1-1 MPa (such as 0.2MPa, 0.5MPa and 0.8MPa), maintaining the pressure for 1-10 min (such as 2min, 4min, 6min and 8min), then placing the obtained product into a hot pressing furnace or a discharge plasma sintering furnace after pressure relief, sintering and forming, wherein the loading pressure of the hot pressing furnace is 30-50 MPa (such as 35MPa, 40MPa and 45MPa), the load on the surface of a sample of the discharge plasma sintering furnace is 50-80 MPa (such as 60MPa, 65MPa, 70MPa and 75MPa), the sintering temperature is 1000-1550 ℃ (such as 1100 ℃, 1200 ℃ and 1400 ℃), the heating rate is 10-50K/min (such as 20K/min, 30K/min and 40K/min), the heat preservation time is 30-600 min (such as 50min, 100min, 200min, 300min, 400min and 500min), and the cooling rate is not more than 25K/min at 800 ℃, the blank body can crack when the cooling speed is too high; in the specific embodiment of the invention, the inner diameter of the graphite mold used in the spark plasma sintering furnace is not more than 50 mm; the inner diameter of the graphite mold used in the hot pressing furnace is not more than 100 mm.

For preparing the rare earth sulfide high-entropy ceramic block with a complex shape or a large size, the sintering molding comprises the following specific steps: placing high-purity sesqui rare earth sulfide high-entropy ceramic powder in a stainless steel mold or a hard alloy mold for cold press molding, wherein the pressure is 35-50MPa (such as 40MPa, 45MPa and 48MPa), the pressure is maintained for 1-5min (such as 2min, 3min and 4min), placing the cold press molded sesqui rare earth sulfide high-entropy ceramic block on a high-strength graphite plate paved with an isolating agent (the isolating agent is used for preventing the ceramic powder from being bonded with the graphite plate in the sintering process and influencing the purity of the ceramic material), then placing the cold press molded sesqui rare earth sulfide high-entropy ceramic block in a pressurizable atmosphere furnace for sintering, wherein the sintering temperature is 1300-1550 ℃ (such as 1400 ℃, 1500 ℃, 1530 ℃ and the heating rate is 10-25K/min (such as 15K/min, 18K/min, 20K/min and 22K/min), the heat preservation time is 20-120 min (such as 30min, 50min, 100min and 110min), and the pressure of the pressure maintaining gas is 5-15 MPa (such as 6MPa, 45MPa, 48MPa), 8MPa, 10MPa and 12MPa), the highest pressure of the atmosphere furnace is not more than 20MPa, and the cooling rate above 800 ℃ is not more than 15K/min.

The application of the high-entropy sesqui-rare earth sulfide ceramic material prepared by the preparation method of the high-entropy sesqui-rare earth sulfide ceramic material is applied to high-temperature thermoelectric functional ceramic materials.

In the following embodiments of the present invention, the diameter of the grinding ball used in the ball milling process is 5 to 22 mm.

Example 1

The preparation method of the high-entropy sesqui-rare earth sulfide ceramic material provided by the embodiment comprises the following steps:

0.276g of Sc was weighed out separately₂O₃、0.452g Y₂O₃、0.652g La₂O₃、0.688g CeO₂、0.6814gPr₆O₁₁(the molar ratio is 1:1:1:1:1), adding the mixture into a stainless steel ball milling tank, weighing 50g of stainless steel balls, adding the stainless steel balls into the ball milling tank, adding 150mL of absolute ethyl alcohol, sealing the ball milling tank by using a sealing gasket, fixing the ball milling tank on a planetary ball mill, and setting ball milling parameters: the rotating speed is 140r/min, the ball milling is carried out for 72h, and the positive and negative rotating directions are adjusted at intervals of 10 minutes. After the ball milling is finishedAnd transferring the slurry and the steel balls into a constant-temperature oil bath pan after the ball milling is finished, setting the temperature to be 80 ℃, slowly stirring to finish the volatilization of the absolute ethyl alcohol, and then sieving the obtained solid mixture to obtain an initial vulcanization precursor.

Weighing 2g of initial vulcanization precursor, placing the initial vulcanization precursor in a quartz crucible, transferring the quartz crucible into a vacuum tube furnace, sealing quartz flanges at two sides of the tube furnace, performing air extraction and inflation cyclic treatment for 3 times, setting the flow of sulfur-containing mixed gas to be 50mL/min after inflation is completed, heating to 800 ℃ at the speed of 10 ℃/min, preserving heat for 3h, and cooling to room temperature along with the furnace under the protection of argon atmosphere after heat preservation is completed. Cooling the tube furnace to room temperature, taking out the quartz crucible, grinding the sintering mixture in a mortar, and then sieving with a 200-mesh sieve to obtain the high-entropy ceramic powder (Sc) containing the sesquialter rare earth sulfide_0.4 Y_0.4La_0.4Ce_0.4 Pr _0.4)S₃。

For high entropy ceramic powder (Sc) of sesqui-rare earth sulfide_0.4 Y_0.4La_0.4Ce_0.4 Pr _0.4)S₃Subjecting the powder to heat treatment to obtain 1g of (Sc)_0.4 Y_0.4La_0.4Ce_0.4 Pr _0.4)S₃Placing the powder in a boron nitride crucible, placing the boron nitride crucible in a high-vacuum atmosphere tube furnace connected with a mechanical pump, a diffusion pump or a molecular pump for heat treatment, preheating a vacuum pump for 15-20 min, and then vacuumizing to 7 multiplied by 10^-3Pa, heating to 1550 ℃ under a vacuum state, keeping the temperature for 9 hours, cooling to room temperature, and taking out to obtain the high-entropy ceramic powder of the high-purity rare earth sulfide.

1g of high-purity rare earth sulfide high-entropy ceramic powder (Sc) after heat treatment_0.4 Y_0.4La_0.4Ce_0.4 Pr _0.4)S₃Placing in a graphite mold, pre-pressing on a tablet press to form, wherein the cold pressure on the surface of the test block is 1MPa, and the pressure maintaining time is 5 min; placing the graphite mold into a hot pressing furnace or a discharge plasma sintering furnace after pressure relief, heating to 1550 ℃ under the protection of argon atmosphere or in a vacuum state, heating at a rate of 25K/min, keeping the temperature for 60min, cooling at a rate of 10K/min above 800 ℃, cooling to room temperature, and taking out to obtain a circleThe high-entropy ceramic block of the cylindrical rare earth sulfide.

And (3) performance testing, namely testing various performances of the sintered sample after cutting and polishing: XRD test, SEM test, thermal conductivity test and electric conductivity test. The resistivity and lattice thermal conductivity of the rare earth sulfide high-entropy ceramic bulk prepared in this example are respectively shown in table 1 below. (Sc)_0.4 Y_0.4La_0.4Ce_0.4 Pr _0.4)S₃The lattice thermal conductivity at 773K is as low as 0.767W/(m.K). The element solid solution can not only optimize the resistivity of the material by adjusting the carrier concentration, but also greatly reduce the lattice thermal conductivity of the sample by increasing the entropy value of the system caused by multi-element solid solution.

FIG. 1 shows a single-phase high-entropy ceramic (Sc) of rare earth sesquisulfide prepared in this example_0.4Y_0.4La_0.4Ce_0.4Pr_0.4)S₃The SEM figure shows that the structure of the sintered cake is uniform and the grain size is about 0.5-1 μm. As shown in FIG. 2 is (Sc)_0.4 Y_0.4La_0.4Ce_0.4Pr_0.4)S₃The energy spectrum surface scanning element distribution diagram of the sintered block, namely the SEM-EDX surface scanning element distribution diagram, shows that five rare earth elements of Sc, Y, La, Ce and Pr are uniformly distributed.

Example 2

The preparation method of the high-entropy sesqui-rare earth sulfide ceramic material provided by the embodiment comprises the following steps:

0.916g of La was weighed out separately₂(CO₃)₃、0.92g Ce₂(CO₃)₃、0.924g Pr₂(CO₃)₃、0.936g Nd₂(CO₃)₃、0.96g Sm₂(CO₃)₃(the molar ratio is 1:1:1:1:1), adding the mixture into a stainless steel ball milling tank, weighing 50g of stainless steel balls, adding the stainless steel balls into the ball milling tank, adding 180mL of distilled water, sealing the ball milling tank by using a sealing gasket, fixing the ball milling tank on a planetary ball mill, and setting ball milling parameters: the rotating speed is 600r/min, the ball milling is carried out for 24 hours, and the positive and negative rotating directions are adjusted at intervals of 10 minutes. After the ball milling is finished, the slurry is mixed with the slurryAnd transferring the steel ball into a constant-temperature oil bath pan, setting the temperature to be 110 ℃, slowly stirring to complete the volatilization of distilled water, and sieving the obtained solid mixture to obtain an initial rare earth carbonate mixture, namely an initial vulcanization precursor.

Weighing 20g of rare earth carbonate mixture, placing the mixture in a quartz crucible, transferring the quartz crucible into a vacuum tube furnace, sealing quartz flanges at two sides of the tube furnace, setting the flow of sulfur-containing mixed gas to be 50mL/min, heating to 880 ℃ at 10 ℃/min, preserving heat for 5h, and cooling to room temperature along with the furnace under the protection of argon after the heat preservation is finished. Cooling the tube furnace to room temperature, taking out the quartz crucible, grinding the sintering mixture in a mortar, and sieving with a 300-mesh sieve to obtain the high-entropy ceramic powder (La) containing the sesqui-rare earth sulfide_0.4Ce_0.4Pr _0.4Nd_0.4Sm_0.4)S₃。

Para-sesqui-rare earth sulfide high-entropy ceramic powder (La)_0.4Ce_0.4Pr_0.4Nd_0.4Sm_0.4)S₃The powder was heat-treated, and 2g (La) was added_0.4Ce_0.4 Pr _0.4Nd_0.4Sm_0.4)S₃Placing the powder in a boron nitride crucible, placing the boron nitride crucible in a high-vacuum atmosphere tube furnace connected with a mechanical pump, a diffusion pump or a molecular pump for heat treatment, preheating a vacuum pump for 15-20 min, and then vacuumizing to 7 multiplied by 10^-3Pa, heating to 1500 ℃ in a vacuum state, keeping the temperature for 12h, cooling to room temperature, and taking out to obtain the high-entropy ceramic powder of the high-purity rare earth sulfide.

2g of heat-treated high-purity rare earth sulfide high-entropy ceramic powder (La)_0.4Ce_0.4Pr _0.4Nd_0.4Sm_0.4)S₃Placing in a graphite mold, pre-pressing on a tablet press to form, wherein the cold pressure on the surface of the test block is 1MPa, and the pressure maintaining time is 5 min; and (3) after pressure relief, placing the graphite mold into a hot pressing furnace, heating to 1500 ℃ under the protection of argon atmosphere or in a vacuum state, heating at a heating rate of 15K/min, keeping the temperature for 60min, cooling to 10K/min at a cooling rate of over 800 ℃, cooling to room temperature, and taking out to obtain the cylindrical rare earth sulfide high-entropy ceramic block.

Performance testingSimilar to example 1, the resistivity and lattice thermal conductivity of the high-entropy ceramic block of the sesqui-rare earth sulfide prepared in this example are respectively shown in table 1 below. High entropy ceramic of sesqui rare earth sulfide (La)_0.4Ce_0.4 Pr _0.4Nd_0.4Sm_0.4)S₃At 773K, the thermal conductivity of crystal lattice is as low as 0.721W/(m.K), and the resistivity can reach 0.00483 omega cm.

FIGS. 3 and 4 are respectively the single-phase sesqui-rare earth sulfide high-entropy ceramics (La) prepared_0.4Ce_0.4 Pr _0.4Nd_0.4Sm_0.4)S₃SEM figure and energy spectrum surface scanning element distribution diagram (SEM-EDX), the SEM figure shows that the texture of the sintered compact is uniform, and the five rare earth elements La, Ce, Pr, Nd, and Sm are also capable of forming single-phase high-entropy ceramics.

Example 3

The preparation method of the high-entropy sesqui-rare earth sulfide ceramic material provided by the embodiment comprises the following steps:

weighing 1.244g Y respectively₂(C₂O₄)₃·10H₂O、1.444g La₂(C₂O₄)₃·10H₂O、1.412g Ce₂(C₂O₄)₃·9H₂O、1.308g Pr₂(C₂O₄)₃·6H₂O、1.464g Nd₂(C₂O₄)₃·10H₂Adding O (which meets the molar ratio of 1:1:1:1:1), weighing 50g of stainless steel balls, adding into a ball milling tank, adding 250mL of distilled water, sealing the ball milling tank by using a sealing gasket, fixing on a planetary ball mill, and setting ball milling parameters: the rotating speed is 600r/min, the ball milling is carried out for 24 hours, and the positive and negative rotating directions are adjusted at intervals of 10 minutes. And after finishing ball milling, transferring the slurry and the steel balls into a constant-temperature oil bath pan after finishing ball milling, setting the temperature at 110 ℃, finishing volatilization of distilled water by slow stirring, and sieving the obtained solid mixture to obtain an initial rare earth oxalate mixture, namely an initial vulcanization precursor.

Weighing 30g of rare earth oxalate mixture, placing the mixture in a quartz crucible, and transferring the quartz crucible to a vacuum tube furnaceAnd sealing quartz flanges at two sides of the tube furnace, performing air exhaust and inflation cyclic treatment for 3 times, setting the flow of the sulfur-containing mixed gas to be 50mL/min after inflation is completed, heating to 900 ℃ at the speed of 10 ℃/min, preserving heat for 9h, and cooling to room temperature along with the furnace under the protection of argon after heat preservation is completed. Cooling the tube furnace to room temperature, taking out the quartz crucible, grinding the sintering mixture in a mortar, and sieving with a 300-mesh sieve to obtain the high-entropy ceramic powder (Y) containing the sesquialter rare earth sulfide_0.4La_0.4Ce_0.4 Pr _0.4Nd_0.4)S₃。

Para-sesqui-rare earth sulfide high-entropy ceramic powder (Y)_0.4La_0.4Ce_0.4 Pr _0.4Nd_0.4)S₃The powder was heat-treated to obtain 3g of (Y)_0.4La_0.4Ce_0.4 Pr _0.4Nd_0.4)S₃Placing the powder in a boron nitride crucible, placing the boron nitride crucible in a high-vacuum atmosphere tube furnace connected with a mechanical pump, a diffusion pump or a molecular pump for heat treatment, preheating a vacuum pump for 15-20 min, and then vacuumizing to 7 multiplied by 10^-3Pa, heating to 1450 ℃ in a vacuum state, keeping the temperature for 10h, cooling to room temperature, and taking out to obtain the high-entropy ceramic powder of the high-purity rare earth sulfide.

3g of high-purity rare earth sulfide high-entropy ceramic powder (Y) after heat treatment_0.4La_0.4Ce_0.4Pr_0.4Nd_0.4)S₃Placing in a graphite mold, pre-pressing on a tablet press to form, wherein the cold pressure on the surface of the test block is 1MPa, and the pressure maintaining time is 5 min; and (2) after pressure relief, placing the graphite mold into a discharge plasma sintering furnace, heating to 1550 ℃ under the protection of argon atmosphere or in a vacuum state, heating to a temperature below 600 ℃ at a heating rate of 10K/min, heating to a temperature above 600 ℃ at a heating rate of 50K/min, keeping the temperature for 60min, cooling to a temperature above 800 ℃ at a cooling rate of 10K/min, cooling to room temperature, and taking out to obtain the cylindrical rare earth sulfide high-entropy ceramic block.

Performance tests similar to example 1, the resistivity and lattice thermal conductivity of the high-entropy ceramic block of the sesqui-rare earth sulfide prepared in this example are shown in table 1 below, respectively. High entropy ceramic of sesqui rare earth sulfide (Y)_0.4La_0.4Ce_0.4 Pr _0.4Nd_0.4)S₃At 773K, the thermal conductivity of crystal lattice is as low as 0.718W/(m.K), and the resistivity can reach 0.00478 mu omega.m.

FIGS. 5 and 6 are respectively the single-phase sesqui-rare earth sulfide high-entropy ceramics (Y)_0.4La_0.4Ce_0.4Pr_0.4Nd_0.4)S₃SEM picture and energy spectrum surface-scan element distribution diagram (SEM-EDX), the SEM picture shows that five rare earth elements of Y, La, Ce, Pr, and Nd can form a single-phase high-entropy ceramic similarly to example 1 and example 2.

Example 4

The preparation method of the high-entropy sesqui-rare earth sulfide ceramic material provided by the embodiment comprises the following steps:

0.706g Y (NO) was weighed out separately₃)₃·10H₂O、0.806g La(NO₃)₃·10H₂O、0.868g Ce(NO₃)₃·9H₂O、0.872g Pr(NO₃)₃·6H₂O、0.888g Sm(NO₃)₃·10H₂Adding O (which meets the molar ratio of 1:1:1:1:1) into a 500mL beaker, wherein the distilled water contains 200mL, then placing the beaker on a constant-temperature magnetic stirrer at 100 ℃, sequentially adding 9.6g of citric acid and 12.4g of ethylene glycol, stirring for 2h, then continuing stirring for 2h at 150 ℃ to generate rare earth gel, transferring the generated rare earth gel into a corundum crucible, calcining for 2h at 300 ℃ in a muffle furnace, then continuing heating to 500 ℃ at the heating rate of 10K/min, and preserving heat for 24h to obtain a mixed rare earth oxycarbonate precursor, namely a multi-element rare earth sulfide precursor.

Weighing 40g of mixed rare earth oxycarbonate precursor, placing the mixed rare earth oxycarbonate precursor in a quartz crucible, transferring the quartz crucible into a vacuum tube furnace, sealing quartz flanges at two sides of the tube furnace, performing air extraction and inflation cyclic treatment for 3 times, setting the Ar flow to be 50mL/min after inflation is finished, heating to 950 ℃ at the speed of 10 ℃/min, preserving heat for 12 hours, and cooling to room temperature along with the furnace under the protection of argon atmosphere after heat preservation is finished. Cooling the tube furnace to room temperature, taking out the quartz boat, grinding the sintering mixture in a mortar, and sieving with a 200-mesh sieve to obtain the high-entropy sesqui-rare earth sulfide ceramic powder (Y_0.4La_0.4Ce_0.4Pr _0.4Sm_0.4)S₃。

Para-sesqui-rare earth sulfide high-entropy ceramic powder (Y)_0.4La_0.4Ce_0.4Pr_0.4Sm_0.4)S₃The powder was heat-treated to obtain 1.5g of (Y)_0.4La_0.4Ce_0.4Pr_0.4Sm_0.4)S₃Placing the powder in a boron nitride crucible, placing the boron nitride crucible in a high-vacuum atmosphere tube furnace connected with a mechanical pump and a diffusion pump or a molecular pump for heat treatment, preheating a vacuum pump for 15-20 min, and then vacuumizing to 7 multiplied by 10^-3Pa, heating to 1400 ℃ in a vacuum state, keeping the temperature for 7.5h, cooling to room temperature, and taking out to obtain the high-purity rare earth sulfide high-entropy ceramic powder.

4g of high-purity rare earth sulfide high-entropy ceramic powder (Y) after heat treatment_0.4La_0.4Ce_0.4Pr_0.4Sm_0.4)S₃Placing in a graphite mold, pre-pressing on a tablet press to form, wherein the cold pressure on the surface of the test block is 1MPa, and the pressure maintaining time is 5 min; and after pressure relief, placing the graphite mold into a hot pressing furnace or a discharge plasma sintering furnace, heating to 1400 ℃ under the protection of argon atmosphere, heating at a heating rate below 600 ℃ of 10K/min, heating at a heating rate above 600 ℃ of 50K/min, keeping the temperature for 60min, cooling at a cooling rate above 800 ℃ of 10K/min, cooling to room temperature, and taking out to obtain the cylindrical rare earth sulfide high-entropy ceramic block.

Performance tests similar to example 1, the resistivity and lattice thermal conductivity of the high-entropy ceramic block of the sesqui-rare earth sulfide prepared in this example are shown in table 1 below, respectively. High entropy ceramic of sesqui rare earth sulfide (Y)_0.4La_0.4Ce_0.4Pr_0.4Sm_0.4)S₃At 773K, the thermal conductivity of crystal lattice is as low as 0.695W/(m.K), and the resistivity can reach 0.00472 omega cm.

FIGS. 7 and 8 are respectively the single-phase sesqui-rare earth sulfide high-entropy ceramics (Y)_0.4La_0.4Ce_0.4Pr_0.4Sm_0.4)S₃SEM picture and energy spectrum surface scanning element distribution diagram (SEM-EDX), the SEM picture shows five rare earth elements of Y, La, Ce, Pr and Sm,the single-phase high-entropy ceramic can be formed by adopting similar processes and different raw materials.

Example 5

The preparation method of the high-entropy sesqui-rare earth sulfide ceramic material provided by the embodiment comprises the following steps:

separately weighing 1.208g YCl₃·6H₂O、1.48g LaCl₃·7H₂O、1.484g CeCl₃·7H₂O、1.488g PrCl₃·6H₂O、1.616g YbCl₃·10H₂Adding O (which meets the molar ratio of 1:1:1:1:1) into a 1000mL beaker, wherein the distilled water in the beaker is 175mL, placing the beaker on a constant-temperature magnetic stirrer at 100 ℃, sequentially adding 9.6g of citric acid and 12.4g of ethylene glycol, stirring for 2h, then continuing stirring for 2h at 150 ℃ to generate gel, transferring the generated gel into a corundum crucible, calcining for 2h at 300 ℃ in a muffle furnace, then continuing heating to 500 ℃ at the heating rate of 10K/min, and preserving heat for 24h to obtain a mixed rare earth oxycarbonate precursor, namely a multi-element rare earth sulfide precursor.

Weighing 5g of mixed rare earth oxycarbonate precursor, placing the mixed rare earth oxycarbonate precursor in a quartz crucible, transferring the quartz crucible into a vacuum tube furnace, sealing quartz flanges at two sides of the tube furnace, performing air exhaust and inflation cyclic treatment for 3 times, setting the Ar flow to be 50mL/min after inflation is finished, heating to 1000 ℃ at the speed of 10 ℃/min, preserving heat for 5 hours, and cooling to room temperature along with the furnace under the protection of argon atmosphere after heat preservation is finished. Cooling the tube furnace to room temperature, taking out the quartz boat, grinding the sintering mixture in a mortar, and sieving with a 600-mesh sieve to obtain the high-entropy ceramic powder (Y) containing the sesquialter rare earth sulfide_0.4La_0.4Ce_0.4 Pr _0.4Yb_0.4)S₃。

Para-sesqui-rare earth sulfide high-entropy ceramic powder (Y)_0.4La_0.4Ce_0.4 Pr _0.4Yb_0.4)S₃The powder was heat-treated to obtain 1.5g of (Y)_0.4La_0.4Ce_0.4 Pr _0.4Yb_0.4)S₃Placing the powder in a boron nitride crucible, placing the boron nitride crucible in a high vacuum atmosphere tube furnace connected with a mechanical pump and a molecular pump for heat treatment, and preheating a vacuum pump15-20 min, then vacuumizing to 7 x 10^-3Pa, heating to 1500 ℃ in a vacuum state, keeping the temperature for 9 hours, cooling to room temperature, and taking out to obtain the high-entropy ceramic powder of the high-purity rare earth sulfide.

3g of high-purity rare earth sulfide high-entropy ceramic powder (Y) after heat treatment_0.4La_0.4Ce_0.4 Pr _0.4Yb_0.4)S₃Placing in a graphite mold, pre-pressing on a tablet press to form, wherein the cold pressure on the surface of the test block is 1MPa, and the pressure maintaining time is 5 min; and after pressure relief, placing the graphite mold into a hot pressing furnace or a discharge plasma sintering furnace, heating to 1550 ℃ under the protection of argon atmosphere or in a vacuum state, heating to a temperature below 600 ℃ at a heating rate of 10K/min, heating to a temperature above 600 ℃ at a heating rate of 50K/min, keeping the temperature for 60min, cooling to a temperature above 800 ℃ at a cooling rate of 10K/min, cooling to room temperature, and taking out to obtain the cylindrical rare earth sulfide high-entropy ceramic block.

Performance tests similar to example 1, the resistivity and lattice thermal conductivity of the high-entropy ceramic block of the sesqui-rare earth sulfide prepared in this example are shown in table 1 below, respectively. High entropy ceramic of sesqui rare earth sulfide (Y)_0.4La_0.4Ce_0.4 Pr _0.4Nd_0.4)S₃At 773K, the thermal conductivity of crystal lattice is as low as 0.00463W/(m.K), and the resistivity can reach 0.675 omega cm.

Example 6

This example differs from example 5 in that 0.842g of Gd (NO) was weighed out separately₃)₃·6H₂O、0.846g Tb(NO₃)₃·6H₂O、0.854g Dy(NO₃)₃·6H₂O、0.858g Ho(NO₃)₃·6H₂O、0.862g Er(NO₃)₃·6H₂Adding O (meeting the molar ratio of 1:1:1:1:1) into a 1000mL beaker, wherein the distilled water in the beaker is 200mL, then placing the beaker on a constant-temperature magnetic stirrer at 100 ℃, sequentially adding 9.6g of citric acid and 12.4g of ethylene glycol, stirring for 2h, then continuing stirring for 2h at 150 ℃ to generate gel, transferring the generated gel into a corundum crucible, calcining for 2h at 300 ℃ in a muffle furnace, then continuing heating to 500 ℃ at the heating rate of 10K/min, and preserving heat for 24h to obtain the multicomponent rare earth before vulcanizationAnd (4) driving the body. The other steps are the same as those in embodiment 5, and are not described herein again.

The resistivity and lattice thermal conductivity of the high-purity sesqui-rare earth sulfide high-entropy ceramic block prepared in this example are respectively shown in table 1 below. High entropy ceramic of sesqui rare earth sulfide (Gd)_0.4Tb_0.4Dy_0.4Ho_0.4Er_0.4)S₃At 773K, the thermal conductivity of crystal lattice is as low as 0.00457W/(m.K), and the resistivity can reach 0.655 omega.cm.

Comparative example 1

In this comparative example, five oxides (Sc) added to the ball mill pot in example 1 were used₂O₃、Y₂O₃、La₂O₃、CeO₂、Pr₆O₁₁) Changed to La₂O₃And Gd₂O₃The molar ratio of the raw materials is still 1:1, and other method steps are the same as those in example 1 and are not described again.

Rare earth sulfide residues are found after the observation of the multi-component sesquisulfide prepared in the comparative example, and after sintering, the same electric transport and thermal transport performance tests as those in example 1 are carried out to obtain the multi-component rare earth sulfide prepared in the present example, wherein the electrical resistivity and the thermal conductivity are respectively shown in the following table 1.

As shown in FIG. 9, which is an XRD pattern of the multicomponent rare earth sulfide prepared in this comparative example 1, it can be seen that the XRD pattern contains two structures of the sesqui rare earth sulfide, and the product is a high-entropy ceramic which is not a single-phase structure.

Comparative example 2

In this comparative example, La, which was the raw material in example 1, was used₂O₃Changing into coarse particles La with equal mass₂O₃(the particle size is 200-300 μm), meanwhile, the temperature of the oxide mixture is directly raised to 800 ℃ in a vacuum tube furnace without mechanical ball milling treatment, the temperature is kept for 3 hours for vulcanization treatment, and other method steps are the same as those in example 1 and are not described again.

When the phase analysis was performed on the multicomponent sulfide prepared in this comparative example, lanthanum oxysulfide remained and the vulcanization was not complete even at elevated temperature. After the same sintering test as in example 1 was performed and then the electric transport and thermal transport performance tests were performed, the resistivity and thermal conductivity of the multicomponent rare earth sulfide obtained in this example were respectively as shown in table 1 below.

Comparative example 3

In this comparative example, the high-entropy ceramic powder (Sc) containing the sesquialter rare earth sulfide in example 1_0.4Y_0.4La_0.4Ce_0.4Pr _0.4)S₃The high-entropy ceramic block is obtained by direct discharge plasma sintering without heat treatment, and other method steps are the same as those in embodiment 1 and are not repeated.

After the high-entropy ceramic block prepared in the comparative example is subjected to the same electrical transport and thermal transport performance tests as in example 1, the resistivity and the thermal conductivity of the multicomponent rare earth sulfide prepared in this example are respectively shown in table 1 below.

Comparative example 4

In this comparative example, as a reference control, the same sulfidation process, heat treatment process and sintering process as in example 1 were used, but only lanthanum oxide was used as a raw material without adding other rare earth oxides, and after the electrical transport and thermal transport performance tests, the electrical resistivity and thermal conductivity were respectively shown in table 1 below.

Table 1 resistivity and thermal conductivity performance data in examples and comparative examples

As can be seen from Table 1, the five-component high-purity sesqui-rare earth sulfide high-entropy ceramic material prepared in the embodiment of the invention has lower resistivity and thermal conductivity, is suitable for high-temperature functional ceramic materials, has good structural stability and improves a high-temperature electric heating transport mechanism.

In summary, the following steps: the high-entropy sesqui-rare earth sulfide ceramic also has the following advantages: 1. the in-situ rapid synthesis can be realized, the preparation temperature is low, the single phase can be rapidly synthesized by the optimized raw materials at the temperature of 800-; 2. the preparation is simple in process aspect, the single-time yield of the prepared powder can reach about 100g, and the powder can be produced in batch; the high-entropy ceramic powder of the sesqui-rare earth sulfide is suitable for color modifiers such as pigments, fillers and the like, and is rich in color and non-toxic; 3. the final product has good performance, is suitable for high-temperature thermoelectric functional ceramic materials, has good structural stability, and improves a high-temperature electrothermal transport mechanism.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.