阅读说明：本技术 一种获得宽温域高介电常数的三弛豫态铁电陶瓷的方法 (Method for obtaining three-relaxation-state ferroelectric ceramic with wide temperature range and high dielectric constant ) 是由 高景晖 王妍 徐靖喆 刘泳斌 钟力生 于 2020-06-24 设计创作，主要内容包括：本发明公开了获得宽温域高介电常数的三弛豫态铁电陶瓷的方法,涉及电子材料领域,包括：确定掺杂了离子的钛酸钡体系为BCyTSx,其中,x、y分别指的是BaSnO<Sub>3</Sub>、CaTiO<Sub>3</Sub>所占BCyTSx整体的物质的量的百分比,0≤x≤0.2,y＝0,0.1,0.22；按掺杂离子百分比从小到大的顺序设计三弛豫态钛酸钡系陶瓷材料；制备钛酸钡系陶瓷材料并进行Curie-Weiss拟合；对钛酸钡系陶瓷材料进行分析,找到样品的单斜相、正交相和菱形相的多相共存区域,当有样品同时具备弛豫特性和多相共存区域,此时对应弛豫相变点和三临界点的铁电陶瓷组成成分即为三弛豫态铁电陶瓷材料。本发明在铁电陶瓷材料领域具有普遍性。(The invention discloses a method for obtaining three-relaxation-state ferroelectric ceramics with wide temperature range and high dielectric constant, which relates to the field of electronic materials and comprises the following steps: determining the ion-doped barium titanate system as BCyTSx, wherein x and y refer to BaSnO respectively 3 、CaTiO 3 The percentage of the substance accounting for the whole BCyTSx is that x is more than or equal to 0 and less than or equal to 0.2, and y is 0, 0.1 and 0.22; designing a three-relaxation-state barium titanate ceramic material according to the sequence of the percentage of doped ions from small to large; preparing barium titanate ceramic materials and carrying out Curie-Weiss fitting; analyzing the barium titanate ceramic material to find the multiphase coexisting region of monoclinic phase, orthorhombic phase and rhombohedral phase of the sample, and when the sample has both relaxation property and the multiphase coexisting region, the ferroelectric ceramic composition corresponding to the relaxation phase change point and the triple critical point is the triple relaxation stateFerroelectric ceramic materials. The invention has generality in the field of ferroelectric ceramic materials.)

1. A method of obtaining a wide temperature range high dielectric constant tri-relaxed state ferroelectric ceramic, the method comprising the steps of:

s100, determining an ion-doped barium titanate system (Ba)_1-yCa_y)(Ti_1-xSn_x)O₃Wherein x and y are BaSnO respectively₃、CaTiO₃Occupied (Ba)_1-yCa_y)(Ti_1-xSn_x)O₃Percentage of the total mass;

s200, designing a three-relaxation-state barium titanate ceramic material according to the sequence of the percentage of the doped ions from small to large;

s300, preparing the barium titanate ceramic material and carrying out Curie-Weiss fitting;

s400, analyzing the barium titanate ceramic material, finding out multiphase coexisting regions of a monoclinic phase, an orthorhombic phase and a rhombohedral phase of a sample, and when the sample has relaxation properties and the multiphase coexisting regions at the same time, obtaining the ferroelectric ceramic material in the three relaxation states as the ferroelectric ceramic material corresponding to the relaxation phase change point and the three critical points.

2. The method of claim 1, wherein the doping ion in step S200 is preferably any one of: sn (tin)⁴⁺、Ca²⁺、Zr⁴⁺、La³⁺、Mg²⁺、Hf⁴⁺。

3. The method of claim 1, wherein the preparing in step S300 comprises the steps of:

s1001, weighing BaCO₃、TiO₂、CaCO₃、SnO₂Mixing the powder with a medium and then performing ball milling to obtain first slurry;

s2001, drying the first slurry, sieving, and sintering the obtained mixed powder to obtain a synthesized first powder material;

s3001, screening the first powder, and then ball-milling to obtain a second slurry;

s4001, drying and sieving the second slurry, adding PVA (polyvinyl alcohol) glue to obtain second powder with the particle size of 60-100 meshes, and pressing the second powder into a rough blank by using a tablet press;

s5001, sintering the rough blank to obtain a barium titanate-based ceramic sample.

4. The method of claim 3, wherein the medium is alcohol in step S1001, and the ball milling time is 4-5 h.

5. The method as claimed in claim 3, wherein the sintering temperature in step S2001 is 1300-1400 ℃.

6. The method of claim 3, wherein the ball milling time in step S3001 is 8-10 h.

7. The method of claim 3, wherein step S5001 further comprises: and (3) placing the rough blank in a sintering furnace, heating to 1350 ℃ and 1450 ℃ at the heating rate of 80-100 ℃/h, and sintering for 8-10 hours to obtain the barium titanate ceramic material.

8. The method of claim 1, wherein the method used to perform the material in step S400 is X-ray diffraction.

Technical Field

The invention relates to the field of electronic ceramic materials, in particular to a method for obtaining three-relaxation-state ferroelectric ceramic with wide temperature range and high dielectric constant.

Background

Ferroelectrics are an important component of electrical functional materials, and are widely applied to electronic and electrical equipment due to excellent dielectric properties, electromechanical properties and electrocaloric effect. Such as storage capacitors, solid state cooling devices, etc. With the rapid development of high energy storage density devices and advanced ferroelectric refrigeration devices, the demand for new ferroelectric materials is increasing, and it is required to maintain good temperature stability to adapt to unstable ambient temperature while having high dielectric constant, but the two properties are difficult to occur in one material at the same time. High dielectric constants often occur near the phase transition temperature, but the dielectric constant rapidly decreases at temperatures away from the phase transition temperature, and thus the temperature stability of such materials is poor. Such as BaTiO₃His maximum dielectric constant is 10000, but only occurs at temperatures close to 3K. These make the trade-off between high dielectric properties and temperature stability of the material seem to be difficult to overcome.

The currently common approach to achieve a balance between high dielectric properties and temperature stability is to use a relaxor ferroelectric, which has a structure and properties different from common ferroelectric materials, has polar nano-domains rather than macroscopic ferroelectric domains, and undergoes relaxation phase transitions, which make its structure intrinsically dispersed, and thus it possesses a very broad dielectric constant peak, which crosses the relaxation phase transition, which makes the relaxor ferroelectric have good temperature stability. However, due to the property of ferroelectrics, the dielectric constant tends to decrease while increasing the temperature stability, which is often seen in Pb (Mg)_1/3Nb_2/3)O₃-PbTiO₃，(Ba，Ca)(Ti，Hf)O₃，K_0.5Na_0.5NbO₃-BaTiO₃In the system. Another giant dielectric material seems to solve the problem of high dielectric constant and temperature stability, but this material has high dielectric loss (10-300%) and low breakdown field strength (1-8KV/cm), which makes it possible to obtain a material with a high dielectric constant and a high temperature stabilityMaking it difficult to use in energy storage materials and electrocaloric materials. Therefore, an effective material that has a high dielectric constant over a wide temperature range and can be used in industrial fields is currently lacking.

Recently, studies have shown that the relaxed barium titanate-based ceramic material has a monoclinic phase, an orthorhombic phase and a rhombohedral phase in a polar nano-region, which may cause the material to have various excellent properties, but a multiphase coexistence point and a relaxation phase transition point are in a relative change state, so that a person skilled in the art considers finding a coexistence region (a triple relaxation state) of the multiphase coexistence point and the relaxation phase transition point in the relaxed ferroelectric ceramic material, such that the ceramic material has a wide temperature range and a high dielectric constant.

Disclosure of Invention

In view of the above-mentioned drawbacks of the prior art, the present invention provides a method for obtaining a three-relaxed-state ferroelectric ceramic with wide temperature range and high dielectric constant, so that the ceramic material has wide temperature range and high dielectric constant.

In order to achieve the above object, the present invention provides a method for obtaining a three-relaxed-state ferroelectric ceramic with a wide temperature range and a high dielectric constant, S100, determining the system of ion-doped barium titanate (Ba)_1-yCa_y)(Ti_1-xSn_x)O₃(BCyTSx), wherein x and y respectively refer to BaSnO₃、CaTiO₃Occupied (Ba)_1-yCa_y)(Ti_1-xSn_x)O₃Percentage of the total mass;

s200, designing a three-relaxation-state barium titanate ceramic material according to the sequence of the percentage of the doped ions from small to large;

s300, preparing the barium titanate ceramic material and carrying out Curie-Weiss fitting;

s400, analyzing the barium titanate ceramic material, finding out multiphase coexisting regions of a monoclinic phase, an orthorhombic phase and a rhombohedral phase of a sample, and when the sample has relaxation properties and the multiphase coexisting regions at the same time, obtaining the ferroelectric ceramic material in the three relaxation states as the ferroelectric ceramic material corresponding to the relaxation phase change point and the three critical points.

The invention also provides a preparation method of the barium titanate ceramic material in the step S300, which comprises the following steps:

s1001, weighing BaCO₃、TiO₂、CaCO₃、SnO₂Mixing the powder with a medium and then performing ball milling to obtain first slurry;

s2001, drying the first slurry, sieving, and sintering the obtained mixed powder to obtain a synthesized first powder material;

s3001, screening the first powder, and then ball-milling to obtain a second slurry;

s4001, drying and sieving the second slurry, adding PVA (polyvinyl alcohol) glue to obtain second powder with the particle size of 60-100 meshes, and pressing the second powder into a rough blank by using a tablet press;

s5001, sintering the rough blank to obtain a barium titanate-based ceramic sample.

Compared with the prior art, the invention has the technical advantages that:

(1) the invention provides a method for obtaining three-relaxation-state ferroelectric ceramic, which can improve the temperature stability of the ferroelectric ceramic while keeping good dielectric property, so that the method can be applied to the optimization of the dielectric property of electronic devices such as capacitors and the like, and has excellent applicability in the research and development of materials with wide temperature range and high dielectric constant;

(2) the method has simple steps, is easy to operate, and has universality in the field of ferroelectric ceramic materials.

The conception, the specific structure and the technical effects of the present invention will be further described with reference to the accompanying drawings to fully understand the objects, the features and the effects of the present invention.

Drawings

FIG. 1 is a graph of a Curie-Weiss fitted line of a barium titanate-based ceramic material prepared in accordance with a preferred embodiment of the present invention;

FIG. 2 is a graph showing the relaxation behavior and the crystal phase composition of barium titanate-based ceramic materials prepared according to a preferred embodiment of the present invention in samples with different dopant ion concentrations;

FIG. 3 shows three relaxed states prepared by a preferred embodiment of the present inventionDielectric constant of barium titanate ceramic material_rAs a function of temperature T.

Detailed Description

The invention provides a method for obtaining three-relaxation-state ferroelectric ceramic with wide temperature range and high dielectric constant, which comprises the following steps:

s100, determining an ion-doped barium titanate system (Ba)_1-yCa_y)(Ti_1-xSn_x)O₃BCyTSx for short, wherein x and y refer to BaSnO respectively₃、CaTiO₃Occupied (Ba)_1-yCa_y)(Ti_1-xSn_x)O₃Percentage of the total mass;

s200, designing a three-relaxation-state barium titanate ceramic material according to the sequence of the percentage of doped ions from small to large;

s300, preparing a barium titanate ceramic material and carrying out Curie-Weiss fitting;

s400, analyzing the barium titanate ceramic material, finding out multiphase coexisting regions of a monoclinic phase, an orthorhombic phase and a rhombohedral phase of the sample, and when the sample has both relaxation characteristics and the multiphase coexisting regions, obtaining the ferroelectric ceramic composition corresponding to the relaxation phase change point and the triple critical point as the triple relaxation state ferroelectric ceramic material.

On one hand, the invention provides a method for obtaining a three-relaxation-state ferroelectric ceramic, which can improve the temperature stability of the ferroelectric ceramic while maintaining good dielectric properties, so that the method can be applied to the optimization of the dielectric properties of electronic devices such as capacitors and the like, and has excellent applicability in the development of materials with wide temperature range and high dielectric constant;

on the other hand, the method has simple steps, is easy to operate and has universality in the field of ferroelectric ceramic materials.

In a preferred embodiment, the dopant ions in step S200 are any one of: sn4⁺、Ca²⁺、Zr⁴⁺、La³⁺、M^g2+、Hf⁴⁺。

In a preferred embodiment, the preparation of the barium titanate-based ceramic material in step S300 includes the following steps:

s1001, weighing BaCO₃、TiO₂、CaCO₃、SnO₂Mixing the powder with a medium and then performing ball milling to obtain first slurry;

s2001, drying the first slurry, sieving, and sintering the obtained mixed powder to obtain a synthesized first powder, wherein the sintering in the step is pre-sintering, so that the components of the final sample are relatively uniform;

s3001, screening the first powder, and then ball-milling to obtain a second slurry;

s4001, drying and sieving the second slurry, adding PVA (polyvinyl alcohol) glue to obtain second powder with the particle size of 60-100 meshes, and pressing the second powder into a rough blank by using a tablet press;

s5001, sintering the rough blank to obtain a barium titanate-based ceramic sample.

The sintering temperature is obtained by combining experiments and theories, when the sintering temperature is too low, the sample is insufficiently sintered, the point defect concentration is increased, the lattice constant is increased along with the point defect concentration, and the dielectric property is reduced. When the sintering temperature is too high, the grain boundary moving speed is accelerated, so that the growth rate of some grains is obviously higher than that of other grains, an overburning phenomenon occurs in a sample, the interaction between the grains and the grain boundary is abnormal, the dielectric property is reduced, and the dielectric constant is reduced along with the temperature increase. Similarly, the ball milling time is selected to ensure sufficient ball milling, so that the materials reach the mesh number required by the experiment; the range of the sintering time is selected to ensure that the sintering is sufficient, the sintering time is short, the sintering is insufficient, and if the sintering time is too long, crystal grains can grow too large, so that the density of the material is reduced, and the breakdown performance is obviously reduced.

The particle size determination range of step S4001 requires dense sintering (95% theoretical density) at the sintering temperature. When the grain size is larger, the surface energy is low and the sintering is not compact. The small particle size affects the sintering efficiency, the sintering is not uniform, part of the sample cannot be densified and secondary phases are easily formed.

In a preferred embodiment, the medium in step S1001 is alcohol, and the ball milling time is 4-5 h.

In a preferred embodiment, the sintering temperature in step S2001 is 1300-.

In a preferred embodiment, the ball milling time in step S3001 is 8-10 h.

In a preferred embodiment, the step S5001 further includes: and (3) placing the rough blank in a sintering furnace, heating to 1350 ℃ and 1450 ℃ at the heating rate of 80-100 ℃/h, and sintering for 8-10 hours to obtain the barium titanate ceramic material.

In a preferred embodiment, the method used to perform the process on the material in step S400 is X-ray diffraction.

The preferred embodiments of the present invention will be described below with reference to the accompanying drawings 1 to 3 of the specification so that the technical contents thereof will be more clearly and easily understood. The present invention may be embodied in many different forms of embodiments and the scope of the invention is not limited to the embodiments set forth herein.

The method of the invention is to dope Ca²⁺、Sn⁴⁺Of barium titanate system, i.e. (Ba)_1-yCa_y)(Ti_1-xSn_x)O₃For short, BC_yTS_xThe system is a research object, wherein x and y respectively refer to BaSnO₃、CaTiO₃Occupied (Ba)_1-yCa_y)(Ti_1-xSn_x)O₃Percentage of the total mass. It has been found that the range of the composition of the region exhibiting relaxation characteristics and coexistence of multiple phases is BC_yTS_xIn the system, x is more than or equal to 0 and less than or equal to 0.2, and y is 0, 0.1 and 0.22.

The three-relaxation-state barium titanate ceramic material is designed according to the sequence of the percentage of doped ions from small to large, and the components of each time are sequentially shown in the following table:

TABLE 1 Ca²⁺、Sn⁴⁺The mass ratio of each raw material in the barium titanate doped ceramic body material

Next, Ca is introduced²⁺、Sn⁴⁺Barium titanate doped ceramic bodyThe specific preparation process of the material comprises the following steps:

s1001, Ca according to Table 1²⁺、Sn⁴⁺BaCO is weighed according to the mass ratio of each raw material in the barium titanate doped ceramic body material₃、TiO₂、CaCO₃、SnO₂Mixing the powder with alcohol as a medium, and performing ball milling for 4-5 hours to obtain first slurry;

s2001, drying the first slurry, sieving, and sintering the obtained mixed powder at 1300-1400 ℃ to obtain a synthesized first powder material;

s3001, screening the first powder, and then ball-milling for 8-10 hours to obtain second slurry;

s4001, drying and sieving the second slurry, adding PVA (polyvinyl alcohol) glue to obtain second powder with the particle size of 60-100 meshes, and pressing the second powder into a rough blank by using a tablet press;

s500, placing the rough blank in a sintering furnace, heating to 1350 ℃ and 1450 ℃ at the heating rate of 80-100 ℃/h, and sintering for 8-10 hours to obtain the barium titanate ceramic material.

The prepared barium titanate ceramic material is subjected to Curie-Weiss fitting, the relaxation property of the barium titanate ceramic material is shown in figure 1, gamma is approximately equal to 2, a sample has the relaxation property, then an XRD (X-ray diffraction) technology is adopted to find a multiphase coexistence area, and the multiphase coexistence state and the relaxation property of the components are analyzed, as shown in figure 2. When the component is BC_0.22TS_0.12When the sample has the relaxation property and the multiphase coexistence region, the composition of the barium titanate ceramic is the three-relaxation-state barium titanate ceramic material.

Ca is measured by a dielectric temperature spectrum test system²⁺、Sn⁴⁺Dielectric constant of barium titanate doped ceramic system material_rThe temperature T is shown in FIG. 3. Compared with pure barium titanate, the dielectric constant of the triple-relaxation-state barium titanate ceramic material is improved by one order of magnitude around room temperature; compared with the components of the relaxation type barium titanate ceramic material, the dielectric peak value is still greatly improved, and the dielectric temperature stability is obviously improved, so that the method for obtaining the barium titanate ceramic material in the three relaxation states has the advantages of developing the material with wide temperature range and high dielectric constantHas good therapeutic effect.

Besides, compared with the traditional method for improving the dielectric temperature stability of the barium titanate-based ceramic, the method has the advantages of simple and convenient operation and easy control.

The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.