阅读说明：本技术 电介质陶瓷材料及其制备方法 (Dielectric ceramic material and preparation method thereof ) 是由 陈秀丽 孙聪聪 黎旭 张海林 周焕福 于 2020-07-18 设计创作，主要内容包括：本发明公开了一种电介质陶瓷材料及其制备方法,将纯度为99.8％无水碳酸钠、99％五氧化二铌、99％碳酸钡和98.5％氧化镁原料烘干处理称取倒入球磨罐中,得到混合物；将无水乙醇、混合物、氧化锆以1:1:2质量比进行第一次球磨,烘干过筛；将第一次球磨后的干粉在800-900℃空气中预烧4小时后,研磨过筛；将预烧后的粉料、氧化锆与无水乙醇以1:2:1的质量比进行第二次球磨,烘干；将第二次球磨烘干后的粉体加入5wt％聚乙烯醇进行造粒,用模具和脱模液压机得到成形的陶瓷块体；将陶瓷块体在550℃下排胶4小时,烧结得到电介质陶瓷材料。本发明制备的固溶体陶瓷材料,烧结温度较低,储能性能优异,具有很大的商业应用前景。(The invention discloses a dielectric ceramic material and a preparation method thereof, which comprises the steps of drying, weighing and pouring raw materials of 99.8% of anhydrous sodium carbonate, 99% of niobium pentoxide, 99% of barium carbonate and 98.5% of magnesium oxide into a ball milling tank to obtain a mixture; carrying out primary ball milling on absolute ethyl alcohol, the mixture and zirconia according to the mass ratio of 1:1:2, drying and sieving; pre-burning the dry powder subjected to the first ball milling in air at 900 ℃ for 4 hours at 800-; performing secondary ball milling on the pre-sintered powder, zirconia and absolute ethyl alcohol according to the mass ratio of 1:2:1, and drying; adding 5 wt% of polyvinyl alcohol into the powder subjected to secondary ball milling and drying for granulation, and obtaining a formed ceramic block by using a die and a demolding hydraulic machine; and (3) gelatinizing the ceramic block body at 550 ℃ for 4 hours, and sintering to obtain the dielectric ceramic material. The solid solution ceramic material prepared by the invention has the advantages of lower sintering temperature, excellent energy storage performance and great commercial application prospect.)

1. A method of preparing a dielectric ceramic material, comprising:

drying raw materials of anhydrous sodium carbonate with the purity of 99.8%, niobium pentoxide with the purity of 99%, barium carbonate with the purity of 99% and magnesium oxide with the purity of 98.5% at the temperature of 90 ℃ for 24 hours, weighing the raw materials, and pouring the raw materials into a ball milling tank to obtain a mixture;

carrying out primary ball milling on absolute ethyl alcohol, the mixture and zirconia for 4 hours according to the mass ratio of 1:1:2, drying and sieving to obtain dry powder;

pre-burning the dry powder subjected to the first ball milling in air at 900 ℃ for 4 hours at 800-;

performing secondary ball milling on the pre-sintered powder, zirconia and absolute ethyl alcohol for 4 hours in a mass ratio of 1:2:1, and drying;

adding 5 wt% of polyvinyl alcohol into the powder subjected to secondary ball milling and drying for granulation, and obtaining a formed ceramic block by using a die and a demolding hydraulic machine;

and (3) gelatinizing the ceramic block body at 550 ℃ for 4 hours, and sintering to obtain the dielectric ceramic material.

2. The method of preparing a dielectric ceramic material according to claim 1, wherein after adding 5 wt% of polyvinyl alcohol to the dried powder for granulation, the method further comprises:

sieving through 60 mesh and 120 mesh sieves leaves particles between 120-60 mesh.

3. The method of claim 1, wherein the step of obtaining a shaped ceramic block using a die and a hydraulic press for demolding comprises:

pressing into a cylinder with a diameter of 8mm and a thickness of 1mm under a pressure of 8-10 MPa.

4. The method of claim 1, wherein the step of gelling the ceramic mass at 550 ℃ for 4 hours comprises:

the ceramic block is put in a furnace and heated to 550 ℃ at the speed of 1 ℃/1min, and after heat preservation is carried out for 4 hours, the ceramic block is naturally cooled along with the furnace.

A dielectric ceramic material, characterized in that the chemical formula of the dielectric ceramic material is(1-x)NaNbO₃-xBa(Mg_1/3Nb_2/3)O₃Wherein x is more than or equal to 0.18 and less than or equal to 0.24.

Technical Field

The invention relates to the technical field of dielectric energy storage ceramics, in particular to a dielectric ceramic material and a preparation method thereof.

Background

At present, the primary energy sources are mainly of the type electric (solid-state capacitors, supercapacitors, inductors, etc.), mechanical (motors, inertial energy storage) and chemical (lithium batteries, fuel cells). The solid capacitor has high power density, fast charge and discharge speed and long cycle life as the preferential energy storage mode of pulse power technology, and the dielectric material with high energy storage density has obvious volume reduction (volume efficiency) effect on many power electronic devices, but the energy storage density (W) of the dielectric material_rec) The pulse power device is relatively low, and the requirements of integration, light weight and miniaturization of the pulse power device cannot be met. At present, most capacitors applied to high-power pulse power supplies are foil-type structure capacitors and metallized film capacitors. The former has the problems of low energy storage density, easy fault explosion and the like; the latter has the disadvantages of short service life, small discharge current, etc. Therefore, in order to meet the requirements of special properties such as high energy storage density, long charging and discharging service life, large output current and the like of an energy storage element in a high-power pulse power supply, designing and preparing the high-performance energy storage dielectric material has important significance.

The dielectric materials currently used for solid state capacitors mainly include five major classes of polymers, ceramic-polymer composites, glass-ceramics and ceramics. Dielectric ceramics have moderate breakdown field strengths (E) relative to other energy storage dielectric materials_b) Lower dielectric loss (tan)) The high-temperature-stability energy-storage capacitor has excellent temperature stability and anti-fatigue property, and can better meet the requirements of the fields of aerospace, oil drilling, electromagnetic pulse weapons and the like on the energy-storage capacitor. Dielectric materials have been actively studied for energy storage applications due to their fast charge and discharge rates, aging resistance, and high performance stability in extreme environments, as compared to chemical energy storage devices, such as batteries and supercapacitors. Thus, ceramic dielectric materials are considered to be excellent materials for making high temperature resistant solid state capacitors.

At present, lead-free energy storage ceramic materials are mainly concentrated on BaTiO₃、(Bi_0.5Na_0.5)TiO₃、(K_0.5Na_0.5)NbO₃And the like, however, it is difficult to achieve both high energy storage density and high energy storage efficiency with these materials. Which limits their practical applications. Therefore, designing and preparing the lead-free dielectric energy storage ceramic with high energy storage density and high energy storage efficiency is a technical difficulty faced in the technical field of dielectric energy storage ceramic at present.

Disclosure of Invention

The invention aims to provide a dielectric ceramic material and a preparation method thereof, and aims to provide Ba (Mg)_1/3Nb_2/3)O₃Doped into NaNbO₃In the matrix, low remanent polarization is obtained, and NaNbO is reduced₃The dielectric loss of the ceramic and the doping of impurities improve the compactness of the ceramic, the grain size is smaller, the breakdown field strength of the ceramic is greatly improved, and the ceramic material with high energy storage density and high utilization rate is obtained.

In order to achieve the above object, in a first aspect, the present invention provides a method for preparing a dielectric ceramic material, comprising:

drying raw materials of anhydrous sodium carbonate with the purity of 99.8%, niobium pentoxide with the purity of 99%, barium carbonate with the purity of 99% and magnesium oxide with the purity of 98.5% at the temperature of 90 ℃ for 24 hours, weighing the raw materials, and pouring the raw materials into a ball milling tank to obtain a mixture;

carrying out primary ball milling on absolute ethyl alcohol, the mixture and zirconia for 4 hours according to the mass ratio of 1:1:2, drying and sieving to obtain dry powder;

pre-burning the dry powder subjected to the first ball milling in air at 900 ℃ for 4 hours at 800-;

performing secondary ball milling on the pre-sintered powder, zirconia and absolute ethyl alcohol for 4 hours in a mass ratio of 1:2:1, and drying;

adding 5 wt% of polyvinyl alcohol into the powder subjected to secondary ball milling and drying for granulation, and obtaining a formed ceramic block by using a die and a demolding hydraulic machine;

and (3) gelatinizing the ceramic block body at 550 ℃ for 4 hours, and sintering to obtain the dielectric ceramic material.

In one embodiment, after adding 5 wt% of polyvinyl alcohol to the dried powder for granulation, the method further comprises:

sieving through 60 mesh and 120 mesh sieves leaves particles between 120-60 mesh.

In one embodiment, a shaped ceramic block is obtained using a die and a hydraulic demolding press, comprising:

pressing into a cylinder with a diameter of 8mm and a thickness of 1mm under a pressure of 8-10 MPa.

In one embodiment, the ceramic block is gelled at 550 ℃ for 4 hours, specifically comprising:

the ceramic block is put in a furnace, heated to 550 ℃ within 1 minute and 1 ℃, and naturally cooled along with the furnace after heat preservation for 4 hours.

In a second aspect, the present invention provides a dielectric ceramic material having the formula (1-x) NaNbO₃-xBa(Mg_1/3Nb_2/3)O₃Wherein x is more than or equal to 0.18 and less than or equal to 0.24.

The invention relates to a dielectric ceramic material and a preparation method thereof, which is prepared by Ba (Mg)_1/3Nb_2/3)O₃Doped into NaNbO₃In the matrix, low remanent polarization is obtained, and NaNbO is reduced₃The dielectric loss of the ceramic and the doping of impurities improve the compactness of the ceramic, the grain size is smaller, the breakdown field strength of the ceramic is greatly improved, and the ceramic material with high energy storage density and good utilization rate is obtained.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic flow chart of a method for preparing a dielectric ceramic material according to an embodiment of the present invention.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.

Referring to fig. 1, fig. 1 is a schematic flow chart of a method for preparing a dielectric ceramic material according to an embodiment of the present invention, and specifically, the method for preparing the dielectric ceramic material may include the following steps:

s101, drying raw materials of anhydrous sodium carbonate with the purity of 99.8%, niobium pentoxide with the purity of 99%, barium carbonate with the purity of 99% and magnesium oxide with the purity of 98.5% at 90 ℃ for 24 hours, weighing the raw materials, and pouring the raw materials into a ball milling tank to obtain a mixture;

in the embodiment of the invention, the following calculation and weighing are carried out: anhydrous sodium carbonate Na with the purity of 99.8 percent₂CO₃99% niobium pentoxide Nb₂O₅99% barium carbonate BaCO₃Drying the raw material and 98.5 percent of magnesium oxide MgO at the temperature of 90 ℃ for 24 hours, and then performing the treatment according to the chemical general formula (1-x) NaNbO₃-xBa(Mg_1/3Nb_2/3)O₃And (x is more than or equal to 0.18 and less than or equal to 0.24), weighing the raw materials in sequence according to the stoichiometric ratio, and pouring the raw materials into a ball milling tank in sequence to obtain a mixture.

S102, carrying out primary ball milling on absolute ethyl alcohol, the mixture and zirconia for 4 hours according to the mass ratio of 1:1:2, drying and sieving to obtain dry powder;

in the embodiment of the invention, ball milling: according to the powder, zirconium oxide ZrO₂The mass ratio of the ethanol to the absolute ethyl alcohol is 1:2:1, adding zirconia balls and absolute ethyl alcohol into the powder in sequence, ball-milling for 4 hours by using a ball mill, taking out and placing into a clean culture dish, quickly drying in an oven at the temperature of 100-120 ℃ after grinding, and sieving the powder.

S103, pre-burning the dry powder subjected to the first ball milling in air at 900 ℃ for 4 hours, and then grinding and sieving;

in the embodiment of the invention, preburning: and pre-burning the sieved powder in an alumina crucible, wherein the pre-burning temperature is 900 ℃, the heat preservation time is 4h, and the heating rate is 5 ℃/min.

S104, performing secondary ball milling on the pre-sintered powder, zirconia and absolute ethyl alcohol for 4 hours in a mass ratio of 1:2:1, and drying;

in the embodiment of the invention, the ball milling is carried out for multiple times: and sequentially putting the pre-sintered powder, zirconia and absolute ethyl alcohol into a nylon tank according to the mass ratio of 1:2:1, ball-milling for 4 hours, taking out, pouring into a clean culture dish, and putting into an oven to dry at the temperature of 100-plus-one and 120 ℃.

S105, adding 5 wt% of polyvinyl alcohol into the powder subjected to secondary ball milling and drying for granulation, and obtaining a formed ceramic block by using a die and a demolding hydraulic machine;

in the embodiment of the invention, granulation molding: adding 5 wt% of polyvinyl alcohol (PVA) into the dried powder for granulation, sieving the powder with a 60-mesh sieve and a 120-mesh sieve to leave particles of 120-60 meshes, and pressing the particles into a cylinder with the diameter of 8mm and the thickness of 1mm under the pressure of 8-10 MPa.

And S106, gluing the ceramic block body at 550 ℃ for 4 hours, and sintering to obtain the dielectric ceramic material.

In the embodiment of the invention, rubber discharging: the ceramic block is put in a furnace, heated to 550 ℃ within 1 minute and 1 ℃, and naturally cooled along with the furnace after heat preservation for 4 hours. And (3) sintering: gradually heating the formed biscuit to 1200 ℃ and 1300 ℃ at the speed of 5 ℃/min after removing the glue, preserving the heat for 2 hours, and naturally cooling along with the furnace to obtain the compact ceramic plate. After the sintered sample is treated, the test analysis shows that the solid solution ceramic material prepared by the invention has lower sintering temperature (less than or equal to 1300 ℃) and excellent energy storage performance (higher energy storage density (J)_d) And energy storage efficiency (η)), low loss, high power, no pollution, lower sintering temperature, contribution to the development of integration and miniaturization, and great commercial application prospect.

The preparation method of the dielectric ceramic material comprises the step of dry-pressing and molding the granulated powder under the pressure of 8 MPa. The temperature rise rate during the glue discharging is 1 ℃/min, and the temperature is kept for 4 h. Polishing and silver-coated electrode is prepared by polishing the sintered ceramic wafer to 0.2mm thickness, brushing silver paste on one surface by a silk screen, covering electrode mesh with silver paste on the other surface, heating to 700 deg.C, keeping the temperature for 30min, and naturally cooling with the furnace to obtain the final product.

Table 1 lists 7 specific examples of the different components constituting the invention and their energy storage properties (the preparation of which is described above).

Table 1:

from table 1, it can be seen that the dielectric ceramic material prepared by the present invention has high energy storage density and high energy storage efficiency.

The invention is realized by doping Ba (Mg)_1/3Nb_2/3)O₃In NaNbO₃Polar nano micro areas are formed in the ceramic by induction, and low remanent polarization is obtained; by using

Ratio of possessionThe large polarizability obtains high saturation polarization; in addition, Ba (Mg)_1/3Nb_2/3)O₃The doping can obviously reduce NaNbO₃The dielectric loss of the base ceramic improves the compactness of the base ceramic, reduces the grain size of the base ceramic, further improves the breakdown strength of the base ceramic, and finally obtains a ceramic material with high energy storage density and high energy storage efficiency;

the material is obtained by batching, ball milling, presintering, secondary ball milling, granulation molding, binder removal, sintering, polishing and silver coating electrode; the total energy storage density calculated based on the electric hysteresis loop is 2.66-4.03J/cm³The energy storage efficiency is between 80 and 90 percent; the material is used as a novel environment-friendly lead-free energy storage ceramic material, and has the advantages of high energy storage density, simple preparation process, low cost, no pollution, easiness in large-scale production and the like.

In a second aspect, the present invention provides a dielectric ceramic material having the formula (1-x) NaNbO₃-xBa(Mg_1/3Nb_2/3)O₃Wherein x is more than or equal to 0.18 and less than or equal to 0.24.

In order to obtain high effective energy storage density and energy storage efficiency for dielectric ceramic energy storage materials, it is necessary to increase the polarization P from several aspects_maxDecrease the remanent polarization P_rAnd increase the breakdown strength E_b。

Ba (Mg) introduced by the invention_1/3Nb_2/3)O₃Has the following advantages:

(1)ratio of possession

The large polarizability achieves high saturation polarization.

(2)Ba²⁺And Mg²⁺Into NaNbO₃The A site and the B site of the ceramic break the long-range ordered structure of the ceramic, promote the formation of polar micro-regions and are beneficial to obtaining low residual polarization strength.

(3) The Ba and Mg elements are uniformly distributed in the crystal, so that the crystal has good chemical stability, and is beneficial to reducing dielectric loss and leakage current, and further higher breakdown strength is obtained.

(4)Ba(Mg_1/3Nb_2/3)O₃The introduction of (A) can promote NaNbO₃The sintering of the ceramic obviously reduces the pore content and the grain size, thereby obtaining high breakdown strength.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.