Ferroelectric ceramic with high energy storage density under low electric field condition and preparation method thereof

Abstract

The invention relates to ferroelectric ceramic with high energy storage density under a low electric field condition and a preparation method thereof, the general formula of the ferroelectric ceramic is (1-x) Ba < 0.1 > Na < 0.74 > Sm < 0.02 > Nb < 0.92 > Sn < 0.1 > O < 3-x > BiMg < 2 / 3 > Ta < 1 / 3 > O < 3 >, in the formula, x is greater than or equal to 0.02 and less than or equal to 0.08, and subscript numbers represent the molar ratio of elements. The preparation method comprises the following steps: calculating and weighing materials according to a chemical general formula, then sequentially carrying out primary ball milling, primary sintering, secondary ball milling, granulation, molding, rubber discharging and secondary sintering, and cooling to room temperature along with a furnace after sintering is completed, so as to obtain the ferroelectric ceramic material. According to the prepared ferroelectric ceramic, at the environment temperature of 25 DEG C, the anti-breakdown field intensity change range Eb is larger than or equal to 240 kV / cm and smaller than or equal to 330 kV / cm, the effective energy storage density change range Wrecc is larger than or equal to 1.91 J / cm < 3 > and smaller than or equal to 3.51 J / cm < 3 >, and the energy storage efficiency change range eta is larger than or equal to 71.1% and smaller than or equal to 86.6%.

Description

Technical Field

[0001] The invention relates to the technical field of energy storage ceramic materials, in particular to a ferroelectric ceramic with high energy storage density under low electric field conditions and a preparation method thereof. Background Art

[0002] Lead-free relaxor ferroelectric energy storage ceramics have attracted extensive attention in the field of energy storage technology due to their excellent environmental characteristics and outstanding relaxor ferroelectric properties. Under the excitation of an external electric field, this type of ceramic has a relatively gentle polarization response, and its hysteresis loop is narrow and long, showing the characteristics of low residual polarization intensity, so it usually has a higher energy storage efficiency. The common disadvantage of this type of ceramic is that under the action of a low external electric field, the saturation polarization intensity is low, and the resulting energy storage density is correspondingly low. Therefore, in order to improve the energy storage density of relaxor ferroelectric ceramics under low external electric field conditions, it is necessary to increase its breakdown resistance field strength and the saturation polarization intensity under the action of an external electric field.

[0003] In order to optimize the comprehensive performance of lead-free relaxor ferroelectric energy storage ceramics, researchers have carried out a lot of work in process adjustment and formula improvement. Process adjustment is to adjust the preparation process parameters, focusing on the sintering process and technical parameters, and optimize the shape, size and distribution of ceramic grains through adjustment, but the overall technology is relatively mature and the room for improvement is limited; the formula design is mainly aimed at the ABO3 type perovskite structure, and the purpose of optimizing the phase composition and grain morphology of ceramics is achieved by adjusting the element types and component ratios, focusing on ion doping modification and multi-component composite. Among them, ion doping can adjust the unit cell size and defect structure of the material, change the polarization effect of the material under external electric field conditions, and make it have better energy storage and release capabilities, but due to the small number of ion types, the adjustability is obviously limited; and multi-component composite is to form a composite structure by introducing other functional materials, coordinating the performance of different functional phases in terms of anti-breakthrough field strength and saturation polarization strength, so as to achieve the effect of optimizing the comprehensive energy storage performance. The diversification of its structure and the diversity of composite materials have greatly enriched the formula design scheme, so it is widely favored by researchers. Summary of the invention

[0004] In order to overcome the shortcomings of lead-free relaxor ferroelectric ceramics, such as low saturation polarization strength and low breakdown field strength under low external electric field conditions, the present invention provides a lead-free relaxor ferroelectric composite ceramic material with high energy storage density under low electric field conditions and a preparation method thereof. The present invention uses NaNbO3 as the matrix material and introduces BiMg 2 / 3 Ta 1 / 3 O3 phase composite, and Sm3 + Ion doping modification improves its saturation polarization strength while increasing the breakdown field strength, thereby achieving the purpose of optimizing the ceramic energy storage performance.

[0005] The present invention is specifically implemented by the following technical scheme: according to the present invention, a ferroelectric ceramic with high energy storage density under low electric field conditions is proposed, and its general formula is (1-x)Ba 0.1 Na 0.74 Sm 0.02 Nb 0.92 Sn 0.1 O3-xBiMg 2 / 3 Ta 1 / 3 O3, wherein 0.02≤x≤0.08, and the subscript numbers represent the molar ratio of the elements.

[0006] Furthermore, the ferroelectric ceramic with high energy storage density under low electric field conditions has a breakdown field strength of 300 kV / cm and an energy storage density of up to 3.51 J / cm at a test frequency of 50 Hz and an ambient temperature of 25°C. 3 , the energy storage efficiency reaches 86.6%.

[0007] The ferroelectric ceramics with high energy storage density under the above-mentioned low electric field conditions are prepared by a traditional solid phase sintering method, and the preparation method specifically comprises the following steps: according to the molar ratio of Ba, Na, Sm, Nb, Sn, Bi, Mg, and Ta being (0.1-0.1x): (0.74-0.74x): (0.02-0.02x): (0.92-0.92x): (0.1-0.1x): x: 0.667x: 0.333x, high-purity dry BaCO3, Na2CO3, Sm2O3, Nb2O3, SnO2, Bi2O3, MgO and Ta2O5 are weighed as raw materials respectively, and then a process flow of primary ball milling, primary sintering, secondary ball milling, granulation, molding, debinding and secondary sintering is carried out in sequence. After sintering, the ferroelectric ceramic material with high energy storage density under low electric field conditions is obtained by cooling to room temperature with the furnace.

[0008] Furthermore, the first ball milling specifically includes filling the weighed raw materials into a can and ball milling them, the ball milling medium is anhydrous ethanol, the ball milling speed is 350r / min-450r / min, and the ball milling time is 6h-8h.

[0009] Furthermore, the primary sintering is specifically to dry the slurry after the primary ball milling, pass it through an 80-mesh sieve, put it into a pot, and keep it at 750° C.-850° C. for 2h-4h.

[0010] Furthermore, the secondary ball milling specifically includes filling the powder obtained from the primary sintering into a can for secondary ball milling, the secondary ball milling medium is anhydrous ethanol, the secondary ball milling speed is 350r / min-450r / min, and the ball milling time is 6h-8h.

[0011] Furthermore, the granulation is specifically to dry the slurry obtained by the secondary ball milling and pass it through a 60-mesh sieve, add a polyvinyl alcohol (PVA) aqueous solution, the PVA aqueous solution is 5wt%-7wt% of the mass of the slurry obtained by the secondary ball milling, and then mix them evenly and granulate them, wherein the concentration of the PVA aqueous solution is 5wt%. Wherein, the polyvinyl alcohol (PVA) aqueous solution is a binder.

[0012] Furthermore, the forming is specifically to dry-press the granulated material obtained after granulation at 200MPa-250MPa to prepare a cylindrical blank with a thickness of 1.2mm and a diameter of 10mm.

[0013] Furthermore, the debinding process is to put the cylindrical blank into a bowl and place it in a muffle furnace, heat it to 450°C-550°C at a heating rate of 2°C / min-8°C / min, and keep it at this temperature for 30min-60min.

[0014] Furthermore, the secondary sintering is to place the debinded green body in a muffle furnace, raise the temperature to 980°C-1050°C at 2°C / min-4°C / min, and sinter at this temperature for 3h-5h. After the secondary sintering is completed, cool it to room temperature with the furnace to obtain a ferroelectric ceramic with high energy storage density under low electric field conditions.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] (1) The composite energy storage ceramic material of the present invention is an environmentally friendly material, which is non-toxic to the human body and does not cause heavy metal pollution to the environment.

[0017] (2) No precious metal elements are used in the preparation process of the ceramic material of the present invention, so the production cost is low, which is conducive to promotion and application.

[0018] (3) The ferroelectric composite ceramic of the present invention has excellent comprehensive energy storage performance and strong frequency stability. When the material chemical formula is 0.92Ba 0.1 Na 0.74 Sm 0.02 Nb 0.92 Sn 0.1 O3-0.08BiMg 2 / 3 Ta 1 / 3 When O3 is used, at a test frequency of 50Hz and an ambient temperature of 25℃, the breakdown field strength is 300kV / cm, and the energy storage density is as high as 3.51J / cm 3 The corresponding energy storage efficiency reaches 86.6%, which is more outstanding compared with similar lead-free energy storage ceramic materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 are XRD patterns of the ferroelectric ceramic materials obtained in Examples 1-4 respectively;

[0020] Figure 2 is a SEM image of the ferroelectric ceramic material obtained in Example 1;

[0021] Figure 3 This is a SEM image of the ferroelectric ceramic material obtained in Example 2;

[0022] Figure 4 This is a SEM image of the ferroelectric ceramic material obtained in Example 3;

[0023] Figure 5 This is a SEM image of the ferroelectric ceramic material obtained in Example 4;

[0024] Figure 6 is a hysteresis loop diagram of the ferroelectric ceramic material obtained in Example 1;

[0025] Figure 7 is a hysteresis loop diagram of the ferroelectric ceramic material obtained in Example 2;

[0026] Figure 8 is a hysteresis loop diagram of the ferroelectric ceramic material obtained in Example 3;

[0027] Fig. 9 is a hysteresis loop diagram of the ferroelectric ceramic material obtained in Example 4; DETAILED DESCRIPTION

[0028] In order to better understand the content of the present invention, the present invention will be further described below in conjunction with specific embodiments and drawings. The following embodiments are implemented based on the technology of the present invention, and detailed implementation methods and operating steps are given, but the protection scope of the present invention is not limited to the following embodiments.

[0029] Embodiment 1:

[0030] (1) According to the general formula 0.98Ba 0.1 Na 0.74 Sm 0.02 Nb 0.92 Sn 0.1 O3-0.02BiMg 2 / 3 Ta 1 / 3 O3 calculation, according to the molar ratio of Ba, Na, Sm, Nb, Sn, Bi, Mg, Ta of 0.098:0.725:0.020:0.902:0.098:0.020:0.013:0.007, weigh high-purity dry raw materials BaCO3, Na2CO3, Sm2O3, Nb2O3, SnO2, Bi2O3, MgO and Ta2O5 respectively; put the weighed raw materials into a can and ball mill, the ball milling medium is anhydrous ethanol, the ball milling speed is 400r / min, and the ball milling time is 8h;

[0031] (2) The milled slurry is dried and passed through an 80-mesh sieve, then placed in a pot for primary sintering at a temperature of 800°C for 4 hours; the powder after the primary sintering is placed in a pot for secondary ball milling, the secondary ball milling medium is anhydrous ethanol, the secondary ball milling speed is 400 r / min, and the secondary ball milling time is 8 hours;

[0032] (3) drying the slurry obtained by the secondary ball milling and passing it through a 60-mesh sieve, adding a binder, mixing and granulating, wherein the binder is a 5 wt % polyvinyl alcohol aqueous solution, and the amount of the binder added is 5 % of the mass of the slurry obtained by the secondary ball milling; dry pressing the obtained granules under a pressure of 250 MPa to prepare a cylindrical body with a thickness of 1.2 mm and a diameter of 10 mm;

[0033] (4) The cylindrical green body is put into a pot and placed in a muffle furnace, and the temperature is increased to 500°C at a heating rate of 5°C / min, and the temperature is kept at 500°C for 30 minutes for debinding; the cylindrical green body after debinding is placed in a muffle furnace for sintering, and the temperature is increased to 980°C at a heating rate of 3°C / min, and the temperature is kept at this temperature for 3 hours. After sintering, the green body is cooled to room temperature in the furnace to obtain a ferroelectric ceramic with high energy storage density under low electric field conditions.

[0034] Embodiment 2:

[0035] (1) According to the general formula 0.96Ba 0.1 Na 0.74 Sm 0.02 Nb 0.92 Sn 0.1 O3-0.04BiMg 2 / 3 Ta 1 / 3 O3 calculation, according to the molar ratio of Ba, Na, Sm, Nb, Sn, Bi, Mg, Ta of 0.096: 0.710: 0.019: 0.883: 0.096: 0.040: 0.027: 0.013, weigh high-purity dry raw materials BaCO3, Na2CO3, Sm2O3, Nb2O3, SnO2, Bi2O3, MgO and Ta2O5 respectively; put the weighed raw materials into a can and ball mill, the ball milling medium is anhydrous ethanol, the ball milling speed is 400r / min, and the ball milling time is 8h;

[0036] (2) The milled slurry is dried and passed through an 80-mesh sieve, then placed in a pot for primary sintering at a temperature of 800°C for 4 hours; the powder after the primary sintering is placed in a pot for secondary ball milling, the secondary ball milling medium is anhydrous ethanol, the secondary ball milling speed is 400 r / min, and the secondary ball milling time is 8 hours;

[0037] (3) drying the slurry obtained by the secondary ball milling and passing it through a 60-mesh sieve, adding a binder, mixing and granulating, wherein the binder is a 5 wt % polyvinyl alcohol aqueous solution, and the amount of the binder added is 5 % of the mass of the slurry obtained by the secondary ball milling; dry pressing the obtained granules under a pressure of 250 MPa to prepare a cylindrical body with a thickness of 1.2 mm and a diameter of 10 mm;

[0038] (4) The cylindrical green body is put into a pot and placed in a muffle furnace, and the temperature is increased to 500°C at a heating rate of 5°C / min, and the temperature is kept at 500°C for 30 minutes for debinding; the cylindrical green body after debinding is placed in a muffle furnace for sintering, and the temperature is increased to 1000°C at a heating rate of 3°C / min, and the temperature is kept at this temperature for 3 hours. After sintering, the green body is cooled to room temperature with the furnace, and a ferroelectric ceramic with high energy storage density under low electric field conditions is obtained.

[0039] Embodiment 3:

[0040] (1) According to the general formula 0.94Ba 0.1 Na 0.74 Sm 0.02 Nb 0.92 Sn 0.1 O3-0.06BiMg 2 / 3 Ta 1 / 3 O3 calculation, according to the molar ratio of Ba, Na, Sm, Nb, Sn, Bi, Mg, Ta of 0.094:0.696:0.019:0.865:0.094:0.060:0.040:0.020, weigh high-purity dry raw materials BaCO3, Na2CO3, Sm2O3, Nb2O3, SnO2, Bi2O3, MgO and Ta2O5 respectively; put the weighed raw materials into a can and ball mill, the ball milling medium is anhydrous ethanol, the ball milling speed is 400r / min, and the ball milling time is 8h;

[0041] (2) The milled slurry is dried and passed through an 80-mesh sieve, then placed in a pot for primary sintering at a temperature of 800°C for 4 hours; the powder after the primary sintering is placed in a pot for secondary ball milling, the secondary ball milling medium is anhydrous ethanol, the secondary ball milling speed is 400 r / min, and the secondary ball milling time is 8 hours;

[0042] (3) drying the slurry obtained by the secondary ball milling and passing it through a 60-mesh sieve, adding a binder, mixing and granulating, wherein the binder is a 5 wt % polyvinyl alcohol aqueous solution, and the amount of the binder added is 5 % of the mass of the slurry obtained by the secondary ball milling; dry pressing the obtained granules under a pressure of 250 MPa to prepare a cylindrical body with a thickness of 1.2 mm and a diameter of 10 mm;

[0043] (4) The cylindrical green body is put into a pot and placed in a muffle furnace, and the temperature is increased to 500°C at a heating rate of 5°C / min, and the temperature is kept at 500°C for 30 minutes for debinding; the cylindrical green body after debinding is placed in a muffle furnace for sintering, and the temperature is increased to 1010°C at a heating rate of 3°C / min, and the temperature is kept at this temperature for 3 hours. After sintering, it is cooled to room temperature in the furnace to obtain a ferroelectric ceramic with high energy storage density under low electric field conditions.

[0044] Embodiment 4:

[0045] (1) According to the general formula 0.92Ba 0.1 Na 0.74 Sm 0.02 Nb 0.92 Sn 0.1 O3-0.08BiMg 2 / 3 Ta 1 / 3 O3 calculation, according to the molar ratio of Ba, Na, Sm, Nb, Sn, Bi, Mg, Ta of 0.092:0.681:0.018:0.846:0.092:0.080:0.053:0.027, weigh high-purity dry raw materials BaCO3, Na2CO3, Sm2O3, Nb2O3, SnO2, Bi2O3, MgO and Ta2O5 respectively; put the weighed raw materials into a can and ball mill, the ball milling medium is anhydrous ethanol, the ball milling speed is 400r / min, and the ball milling time is 8h;

[0046] (2) The milled slurry is dried and passed through an 80-mesh sieve, then placed in a pot for primary sintering at a temperature of 800°C for 4 hours; the powder after the primary sintering is placed in a pot for secondary ball milling, the secondary ball milling medium is anhydrous ethanol, the secondary ball milling speed is 400 r / min, and the secondary ball milling time is 8 hours;

[0047] (3) drying the slurry obtained by the secondary ball milling and passing it through a 60-mesh sieve, adding a binder, mixing and granulating, wherein the binder is a 5 wt % polyvinyl alcohol aqueous solution, and the amount of the binder added is 5 % of the mass of the slurry obtained by the secondary ball milling; dry pressing the obtained granules under a pressure of 250 MPa to prepare a cylindrical body with a thickness of 1.2 mm and a diameter of 10 mm;

[0048] (4) The cylindrical green body is put into a pot and placed in a muffle furnace, and the temperature is increased to 500°C at a heating rate of 5°C / min, and the temperature is kept at 500°C for 30 minutes for debinding; the cylindrical green body after debinding is placed in a muffle furnace for sintering, and the temperature is increased to 1020°C at a heating rate of 3°C / min, and the temperature is kept at this temperature for 3 hours. After sintering, it is cooled to room temperature in the furnace to obtain a ferroelectric ceramic with high energy storage density under low electric field conditions.

[0049] After cleaning the ferroelectric ceramic samples prepared in Examples 1-4, X-ray diffractometer (Bruker D8, PANalytical BV, Netherlands) was used to analyze the XRD patterns. Figure 1 .Depend on Figure 1 It can be seen that when BiMg 2 / 3 Ta 1 / When the 3O3 content exceeds 0.04 mol% and continues to increase, the intensity of the diffraction peak in the (200) direction decreases significantly, which means that the lattice constant changes significantly. As the deformation of the unit cell intensifies, the internal stress increases accordingly, and the polarization transition barrier increases, which is beneficial to the improvement of the ceramic's anti-breakdown field strength. The surface SEM images were taken using a scanning electron microscope (SU8010, Hitachi, Japan). The results are shown in Figure 2-5 The grain size of each example sample is mainly affected by two aspects: 2 / 3Ta 1 / 3 The ion substitution after O3 addition causes the unit cell deformation, and the corresponding increase in internal stress is not conducive to the growth of grains; secondly, the introduction of Bi element improves the sintering characteristics. The melting temperature of Bi-containing oxide is low, which is conducive to the migration of other elements during the sintering process, thus promoting the growth of grains. From the SEM image, it can be seen that BiMg 2 / 3 Ta 1 / 3 When the addition of O3 is less than 0.04 mol%, the grain size does not change much; 2 / 3 Ta 1 / 3 When the amount of O3 added increased from 0.04mol% to 0.06mol%, the average grain size decreased significantly, indicating that the internal stress change caused by ion substitution played a dominant role; 2 / 3 Ta 1 / 3 When the amount of O3 added reaches 0.08 mol%, the average grain size increases rapidly, which means that the Bi element content has a significant effect on the sintering characteristics after reaching a certain level. Among them, when the grain size decreases, the grain boundaries increase, and the polarization transition barrier increases accordingly, which is beneficial to the improvement of the sample's anti-breakthrough field strength, while the increase in grain size is beneficial to the improvement of the saturated polarization intensity.

[0050] The ferroelectric ceramic samples prepared in Examples 1-4 were all polished with 1500 mesh corundum until the thickness was 0.1 mm, ultrasonically cleaned and then dried, and high-temperature conductive silver paste was coated on both sides. After drying, the silver electrodes were solidified at 500° C., kept warm for 30 minutes, and then naturally cooled for testing. The hysteresis loops of the samples were measured using a ferroelectric tester (LC II-100V, Radiant, USA) at a test frequency of 50 Hz and an ambient temperature of 25° C. The results are shown in FIG. Figure 6-9 . Using the energy storage density and energy storage efficiency calculation formula and Calculate, where W c , W d ,η,E,P r and P s They respectively refer to charging energy storage density, discharging energy storage density, energy storage efficiency, applied electric field strength, residual polarization strength and saturation polarization strength. The energy storage performance of the ferroelectric ceramic materials in each embodiment is as follows:

[0051] Example 1: Anti-breakthrough field strength E b is 250kV / cm, and the saturation polarization intensity P s 20.34μC / cm 2 , and the energy storage density W is calculated rec 1.91 J / cm 3 , the energy storage efficiency η is 71.05%.

[0052] Example 2: Anti-breakthrough field strength E b is 240kV / cm, and the saturation polarization intensity P s 16.69μC / cm 2 , and the energy storage density W is calculated rec 1.77 J / cm 3 , the energy storage efficiency η is 87.73%.

[0053] Example 3: Anti-breakthrough field strength E b is 330kV / cm, and the saturation polarization intensity P s 21.1μC / cm 2 , and the energy storage density W is calculated rec 2.89 J / cm 3 , the energy storage efficiency η is 78.59%.

[0054] Example 4: Anti-breakthrough field strength E b is 300kV / cm, and the saturation polarization intensity P s 26.41μC / cm 2 , and the energy storage density W is calculated rec 3.51 J / cm 3 , the energy storage efficiency η is 86.6%.

[0055] The above is only an embodiment of the present invention, and does not limit the present invention in any form. The present invention can also have other forms of embodiments according to the above structures and functions, which are not listed one by one. Therefore, any simple modification, equivalent change and modification made by any technician familiar with the profession to the above embodiment according to the technical essence of the present invention without departing from the scope of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A ferroelectric ceramic having high energy storage density under low electric field conditions, characterized in that: The general formula of the ferroelectric ceramic is (1-x)Ba 0.1 Na 0.74 Sm 0.02 Nb 0.92 Sn 0.1 O3-xBiMg 2 / 3 Ta 1 / 3 O3, wherein 0.02≤x≤0.08, and the subscript numbers represent the molar ratio of the elements.

2. The ferroelectric ceramic with high energy storage density under low electric field conditions as claimed in claim 1, characterized in that: The ferroelectric ceramic has a breakdown field strength of 300 kV / cm and an energy storage density of 3.51 J / cm at a test frequency of 50 Hz and an ambient temperature of 25°C. 3 , the energy storage efficiency reaches 86.6%.

3. The method for preparing a ferroelectric ceramic having high energy storage density under low electric field conditions as claimed in claim 1 or 2, characterized in that: The specific steps include: According to the molar ratio of Ba, Na, Sm, Nb, Sn, Bi, Mg and Ta: (0.1-0.1x): (0.74-0.74x): (0.02-0.02x): (0.92-0.92x): (0.1-0.1x): x: 0.667x: 0.333x, high-purity and dry BaCO3, Na2CO3, Sm2O3, Nb2O3, SnO2, Bi2O3, MgO and Ta2O5 are weighed as raw materials respectively, and then the process flow of primary ball milling, primary sintering, secondary ball milling, granulation, molding, debinding and secondary sintering is carried out in sequence. After sintering, the material is cooled to room temperature with the furnace to obtain a ferroelectric ceramic material with high energy storage density under low electric field conditions.

4. The method for preparing a ferroelectric ceramic having high energy storage density under low electric field conditions as claimed in claim 3, characterized in that: The first ball milling specifically includes putting the weighed raw materials into a can and ball milling them, the ball milling medium is anhydrous ethanol, the ball milling speed is 350r / min-450r / min, and the ball milling time is 6h-8h.

5. The method for preparing a ferroelectric ceramic having high energy storage density under low electric field conditions as claimed in claim 3, characterized in that: The primary sintering is specifically to dry the slurry after the primary ball milling, pass it through an 80-mesh sieve, put it into a pot, and keep it at 750° C.-850° C. for 2h-4h.

6. The method for preparing a ferroelectric ceramic having high energy storage density under low electric field conditions as claimed in claim 3, characterized in that: The secondary ball milling specifically includes filling the powder obtained from the primary sintering into a can and performing secondary ball milling, wherein the secondary ball milling medium is anhydrous ethanol, the secondary ball milling speed is 350 r / min-450 r / min, and the ball milling time is 6h-8h.

7. The method for preparing a ferroelectric ceramic having high energy storage density under low electric field conditions as claimed in claim 3, characterized in that: The granulation is specifically to dry the slurry obtained by secondary ball milling and pass it through a 60-mesh sieve, add a polyvinyl alcohol (PVA) aqueous solution, wherein the PVA aqueous solution is 5wt%-7wt% of the mass of the slurry obtained by secondary ball milling, and then mix them evenly and granulate them, wherein the mass fraction of the PVA aqueous solution is 5wt%.

8. The method for preparing a ferroelectric ceramic having high energy storage density under low electric field conditions as claimed in claim 3, characterized in that: The forming is specifically to dry-press the granulated material obtained after granulation at 200 MPa-250 MPa to prepare a cylindrical green body with a thickness of 1.2 mm and a diameter of 10 mm.

9. The method for preparing a ferroelectric ceramic having high energy storage density under low electric field conditions as claimed in claim 3, characterized in that: The debinding process specifically comprises placing the cylindrical blank in a bowl and placing it in a muffle furnace, heating the temperature to 450°C-550°C at a heating rate of 2°C / min-8°C / min, and keeping the temperature at this temperature for 30min-60min.

10. The method for preparing a ferroelectric ceramic having high energy storage density under low electric field conditions as claimed in claim 3, characterized in that: The secondary sintering is to place the debinded green body in a muffle furnace, raise the temperature to 980°C-1050°C at 2°C / min-4°C / min, and sinter at this temperature for 3h-5h. After the secondary sintering is completed, cool it to room temperature with the furnace to obtain a ferroelectric ceramic with high energy storage density under low electric field conditions.

Images