Calcium bismuth titanate-based piezoelectric ceramics and their preparation methods and applications

Abstract

The present invention discloses a calcium bismuth titanate-based piezoelectric ceramic, its preparation method and application. The preparation method of the calcium bismuth titanate-based piezoelectric ceramic includes: mixing a Ca source, a Na source, a Ce source, a Bi source, a Ti source, a Co source, a Nb source and a Cr source to obtain a mixed material, mixing the mixed material evenly, and pre-sintering it at 750-900 °C for 2-4 h to obtain a pre-sintered material; mixing the pre-sintered material evenly, granulating, vacuum encapsulating, and isostatic pressing at room temperature to obtain a green body column; subjecting the green body column to debinding treatment, and performing the first sintering at 1000-1300 °C to obtain a ceramic material; coating the ceramic material with high-temperature silver paste, performing the second sintering and high-voltage polarization in silicone oil successively to obtain the calcium bismuth titanate-based piezoelectric ceramic. The calcium bismuth titanate-based piezoelectric ceramic of the present invention has a piezoelectric constant of 24 pC / N, a dielectric loss of 0.12%, and a resistivity of 7.5×10<supgt;6< / supgt> Ω·cm at 600 °C while the Curie temperature is as high as 786 °C.

Description

Technical Field

[0001] The present invention belongs to the technical field of piezoelectric ceramics, and specifically relates to a calcium bismuth titanate-based piezoelectric ceramic, a preparation method thereof, and an application thereof. Background Art

[0002] High-temperature acceleration sensors can be used to monitor some devices in the fields of aerospace, geological exploration, petrochemical industry, automotive engines, etc. at high temperatures in real time. Piezoelectric materials, especially high-temperature piezoelectric ceramic materials, are essential for the preparation of high-temperature acceleration sensors.

[0003] Currently, the most widely used high-temperature piezoelectric ceramic material is lead zirconate titanate (PZT)-based piezoelectric ceramic material. However, its Curie temperature is too low, only between 250 and 380 °C, and the safe operating temperature is limited to half of the Curie temperature. Therefore, this type of ceramic can no longer meet the requirements of the current development of high-tech.

[0004] Calcium bismuth titanate (CaBi4Ti4O 15 )-based ceramic materials are also often used in high-temperature acceleration sensors. Its Curie temperature is as high as 790 °C, and the piezoelectric constant d 33 is about 7 pC / N. In practical applications, its piezoelectric constant is too low, and the temperature drift of the piezoelectric constant (i.e., the change of the piezoelectric constant with temperature) is also relatively large. Therefore, how to improve the piezoelectric constant, increase the resistivity, and enhance the thermal stability without sacrificing the Curie temperature of CaBi4Ti4O 15 -based ceramic materials is a key issue. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a preparation method of a calcium bismuth titanate-based piezoelectric ceramic. The preparation method first dopes (NaCe) 15 composite ions (Na and Ce simultaneously replace the A site in the crystal) at the A site in the calcium bismuth titanate (CaBi4Ti4O 5+ )-based ceramic material, dopes (Co 1 / 2 Nb 1 / 2 ) 4+ composite ions (Co and Nb simultaneously replace the B site in the crystal) at the B site, and on this basis, externally dope Cr2O3 for modification (not participating in substitution) to obtain a calcium bismuth titanate-based piezoelectric ceramic.

[0006] Another object of the present invention is to provide a calcium bismuth titanate-based piezoelectric ceramic obtained by the above preparation method.

[0007] Another object of the present invention is to provide an application of the above calcium bismuth titanate-based piezoelectric ceramic in an acceleration sensor.

[0008] The object of the present invention is achieved by the following technical solutions.

[0009] A preparation method of calcium bismuth titanate-based piezoelectric ceramics, comprising the following steps:

[0010] Step 1: Mix a Ca source, a Na source, a Ce source, a Bi source, a Ti source, a Co source, a Nb source and a Cr source to obtain a mixed material, mix the mixed material evenly, and pre-sinter at 750-900 °C for 2-4 h to obtain a pre-sintered material. Among them, in terms of the number of moles, the ratio of Ca in the Ca source, Na in the Na source, Ce in the Ce source, Bi in the Bi source, Ti in the Ti source, Co in the Co source, Nb in the Nb source and Cr in the Cr source is (0.88-0.98):(0.008-0.048):(0.008-0.048):4:(3.88-3.98):(0.01-0.06):(0.01-0.06):(0.02-0.08);

[0011] In step 1, preferably, in terms of the number of moles, the ratio of Ca in the Ca source, Na in the Na source, Ce in the Ce source, Bi in the Bi source, Ti in the Ti source, Co in the Co source, Nb in the Nb source and Cr in the Cr source is (0.93-0.95):(0.02-0.03):(0.02-0.03):4:(3.93-3.95):(0.025-0.035):(0.025-0.035):0.02.

[0012] In step 1, the Ca source is CaCO3, the Na source is Na2CO3, the Ce source is CeO2, the Bi source is Bi2O3, the Ti source is TiO2, the Co source is Co2O3, the Nb source is Nb2O5, and the Cr source is Cr2O3.

[0013] In step 1, the pre-sintering is carried out in an air environment.

[0014] Step 2: Mix the pre-sintered material evenly, granulate, vacuum package, and isostatically press at room temperature to obtain a green billet column;

[0015] In step 2, an adhesive is used for granulation. In terms of mass parts, the ratio of the adhesive to the pre-sintered material is (2-5):1.

[0016] In the above technical solution, the adhesive is an aqueous solution of polyvinyl alcohol (PVA). The aqueous solution of polyvinyl alcohol (PVA) is a mixture of polyvinyl alcohol (PVA) and water. In terms of mass parts, the ratio of water to polyvinyl alcohol in the aqueous solution of polyvinyl alcohol (PVA) is (15-20):1.

[0017] In step 2, the vacuum packaging includes: pressing and packaging the column at a pressure of 2-4 MPa.

[0018] In step 2, the pressure of the warm isostatic pressing is 30 - 50 MPa, the pressure holding time of the warm isostatic pressing is 10 - 20 s, and the temperature of the warm isostatic pressing is 25 - 40 °C.

[0019] In the above technical solution, the pressure increasing rate of the warm isostatic pressing is 2 - 3 MPa / s.

[0020] In steps 1 and 2, the mixing evenly is carried out by ball milling, the ball milling adopts wet milling, and the medium of the wet milling is anhydrous ethanol.

[0021] In the above technical solution, by mass fraction, the ball - to - material ratio of the ball milling is (3 - 5):1.

[0022] In the above technical solution, after wet milling, drying is carried out. The temperature of the drying is 70 - 80 °C, and the time of the drying is 7 - 8 h.

[0023] In the above technical solution, the rotation speed of the ball milling is 300 - 400 r / min, and the time of the ball milling is 8 - 12 h.

[0024] Step 3: Subject the green body column to debinding treatment, and conduct the first sintering at 1000 - 1300 °C to obtain a ceramic material. Among them, the time of the first sintering is 3 - 5 h;

[0025] In step 3, the temperature of the debinding treatment is 550 - 650 °C, and the time of the debinding treatment is 0.5 - 2 h.

[0026] In the above technical solution, the heating rate for heating to 550 - 650 °C is 3 - 5 °C / min.

[0027] In step 3, the heating rate for heating to 1000 - 1300 °C is 3 - 5 °C / min.

[0028] In step 3, the first sintering is carried out in an air environment.

[0029] Step 4: Subject the ceramic material to coating with high - temperature silver paste (electrode formation), the second sintering (electrode sintering), and high - voltage polarization in silicone oil in sequence to obtain a bismuth calcium titanate - based piezoelectric ceramic.

[0030] In step 4, the second sintering includes: maintaining the temperature at 800 - 850 °C for 10 - 40 min in an air environment.

[0031] In step 4, the high - voltage polarization in silicone oil includes: polarizing in silicone oil at 150 - 200 °C with a polarization field strength of 10 - 12 kV / mm for 30 - 40 min.

[0032] The bismuth calcium titanate - based piezoelectric ceramic obtained by the above preparation method.

[0033] Application of the above-mentioned calcium bismuth titanate-based piezoelectric ceramics in an acceleration sensor.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] 1. In the calcium bismuth titanate-based piezoelectric ceramics of the present invention, the Ca element is replaced by a composite ion (NaCe) 5+ and the Ti element is replaced by a composite ion (Co 1 / 2Nb 1 / 2 ). 4+ Compared with the CaBi4Ti4O 15 -based ceramic material, while ensuring that the Curie temperature does not decrease, the piezoelectric constant and the resistivity at high temperature of the present invention are increased, and the dielectric loss is reduced. The calcium bismuth titanate-based piezoelectric ceramics of the present invention have a piezoelectric constant of 24 pC / N (room temperature), a dielectric loss of 0.12% (room temperature), and a resistivity of 7.5×10 6 Ω·cm at a Curie temperature as high as 786 °C;

[0036] 2. When the calcium bismuth titanate-based piezoelectric ceramics of the present invention are at room temperature to 650 °C, the temperature drift of the piezoelectric constant is within 5.6%, and it can operate stably at 650 °C for a long time;

[0037] 3. When the calcium bismuth titanate-based piezoelectric ceramics of the present invention are at room temperature to 600 °C, the change of the dielectric loss with temperature is small;

[0038] 4. The resistivity of the calcium bismuth titanate-based piezoelectric ceramics of the present invention can reach 7.5×10 6 Ω·cm at 600 °C. Compared with the CaBi4Ti4O 15 -based ceramic material, it is increased by two orders of magnitude at the same temperature, and has great application prospects in the field of high-temperature devices;

[0039] 5. The preparation method of the present invention is simple and the cost is low, which is suitable for large-scale industrial production. Description of the Drawings

[0040] Figure 1 XRD diffraction pattern of the calcium bismuth titanate-based piezoelectric ceramics prepared in Examples 1 to 6;

[0041] Figure 2 Scanning electron microscope images (SEM) of the calcium bismuth titanate-based piezoelectric ceramics prepared in Examples 2 to 5. Among them, (a) to (d) are the SEM images of the calcium bismuth titanate-based piezoelectric ceramics prepared in Examples 2 to 5 in sequence;

[0042] Figure 3 Variation diagram of the dielectric loss with temperature of the calcium bismuth titanate-based piezoelectric ceramics prepared in Examples 1 to 6;

[0043] Figure 4 Variation diagram of dielectric loss of the piezoelectric ceramic materials prepared in Comparative Examples 7 - 12 with temperature;

[0044] Figure 5 Variation diagram of dielectric constant of the calcium bismuth titanate - based piezoelectric ceramic prepared in Example 3 with temperature;

[0045] Figure 6 Variation diagram of piezoelectric constant of the calcium bismuth titanate - based piezoelectric ceramics prepared in Examples 1 - 6 with temperature;

[0046] Figure 7 Variation diagram of piezoelectric constant of the piezoelectric ceramic material prepared in Comparative Example 3 with temperature;

[0047] Figure 8 Variation diagram of piezoelectric constant of the piezoelectric ceramic materials prepared in Comparative Examples 7 - 12 with temperature;

[0048] Figure 9 Variation diagram of resistivity of the calcium bismuth titanate - based piezoelectric ceramics prepared in Examples 1 - 6 with temperature. Detailed implementation manners

[0049] The technical solution of the present invention will be further described below in conjunction with specific embodiments.

[0050] In the following embodiments, the Ca source is CaCO3, the Na source is Na2CO3, the Ce source is CeO2, the Bi source is Bi2O3, the Ti source is TiO2, the Co source is Co2O3, the Nb source is Nb2O5, and the Cr source is Cr2O3. CaCO3, Na2CO3, CeO2, Bi2O3, TiO2, Co2O3, Nb2O5 and Cr2O3 are all of analytical purity.

[0051] High - temperature silver paste: Xi'an Hongxingxing Electronic Paste Technology Co., Ltd., model C - 1002.

[0052] Unless otherwise specified, the following piezoelectric constant, dielectric constant, dielectric loss, and electromechanical coupling coefficient are all detected at room temperature of 20 - 25°C.

[0053] Examples 1 - 6

[0054] A preparation method of a calcium bismuth titanate - based piezoelectric ceramic, comprising the following steps:

[0055] Step 1: Mix the Ca source, Na source, Ce source, Bi source, Ti source, Co source, Nb source and Cr source to obtain a mixed material. Ball mill the mixed material at a speed of 300 r / min for 8 h until it is evenly mixed (wet ball milling is used, and the medium for wet ball milling is anhydrous ethanol. By mass, the ratio of anhydrous ethanol to the mixed material in this step is 4:3. By mass, the ball-to-material ratio for ball milling is 4:1). Dry it at 75 °C for 8 h, and pre-sinter it at 850 °C for 3 h in an air environment to obtain a pre-sintered material. Among them, by the number of moles, the ratio of Ca in the Ca source, Na in the Na source, Ce in the Ce source, Bi in the Bi source, Ti in the Ti source, Co in the Co source, Nb in the Nb source and Cr in the Cr source is A, and the value of A is shown in Table 1;

[0056] Step 2: Ball mill the pre-sintered material at a speed of 300 r / min for 8 h until it is evenly mixed (wet ball milling is used, and the medium for wet ball milling is anhydrous ethanol. By mass, the ratio of anhydrous ethanol to the pre-sintered material in this step is 4:3. By mass, the ball-to-material ratio for ball milling is 4:1). Dry it at 75 °C for 8 h, granulate it, and vacuum package it (use a dry-pressing type tablet press to press and package it at a pressure of 3 MPa). Isostatically press it at 40 °C under a pressure of 40 MPa for 10 s (the pressure increasing rate for isostatic pressing is 3 MPa / s) to obtain a green compact column with a thickness of 13 mm and a diameter of 10 mm. Among them, a binder is used for granulation. By mass, the ratio of the binder to the pre-sintered material is 4:1. The binder is an aqueous solution of polyvinyl alcohol (PVA). The aqueous solution of polyvinyl alcohol (PVA) is a mixture of polyvinyl alcohol (PVA) and water. By mass, the ratio of water to polyvinyl alcohol in the aqueous solution of polyvinyl alcohol (PVA) is 18:1;

[0057] Step 3: Heat the green compact column at a rate of 4 °C / min to 650 °C and perform a debinding treatment at 650 °C for 2 h to remove the binder (at the same time, it can make the ceramic material have a certain hardness). In an air environment, perform the first sintering at 1160 °C (the heating rate to 1160 °C is 4 °C / min) to obtain a ceramic material. Among them, the time for the first sintering is 3 h;

[0058] Step 4: Cut the ceramic material into ceramic slices with a thickness of 0.6 mm. Polish both sides of the ceramic slices with 600-mesh sandpaper. After polishing, coat both sides of the ceramic slices with high-temperature silver paste (electrode coating). In an air environment, keep it at 850 °C for 20 min for the second sintering (electrode sintering). After the second sintering, polish it on A4 paper to remove the surface silver oxide, and polarize it under high pressure in silicone oil to obtain a calcium bismuth titanate-based piezoelectric ceramic. Among them, the high-pressure polarization in silicone oil is to polarize it in silicone oil at 180 °C with a polarization field strength of 11.5 kV / mm for 40 min.

[0059] Table 1

[0060]

[0061] Comparative Examples 1 - 6

[0062] A method for preparing a piezoelectric ceramic material is basically the same as that of Example 1, and the only difference is that: for the mixture, the mixtures of Comparative Examples 1 - 6 are all prepared by mixing a Ca source, a Na source, a Ce source, a Bi source, a Ti source, a Co source, and a Nb source. By mole fraction, the ratio of Ca in the Ca source, Na in the Na source, Ce in the Ce source, Bi in the Bi source, Ti in the Ti source, Co in the Co source, and Nb in the Nb source is B, and the values of B are shown in Table 2.

[0063] Table 2

[0064]

[0065] Comparative Examples 7 - 12

[0066] A method for preparing a piezoelectric ceramic material is basically the same as that of Example 1, and the only difference is that: for the mixture, the mixtures of Comparative Examples 7 - 12 are all prepared by mixing a Ca source, a Ce source, a Bi source, a Ti source, a Co source, a Nb source, and a Cr source. By mole fraction, the ratio of Ca in the Ca source, Ce in the Ce source, Bi in the Bi source, Ti in the Ti source, Co in the Co source, Nb in the Nb source, and Cr in the Cr source is C, and the values of C are shown in Table 3.

[0067] Table 3

[0068]

[0069] The piezoelectric ceramic materials prepared in Comparative Examples 7 - 12 are doped with Ce ions at the A site and (Co 4+ Nb 1 / 2 Nb 1 / 2 ) 4+ composite ions at the B site, and on this basis, Cr2O3 is externally doped (not participating in substitution).

[0070] Comparative Example 13

[0071] A calcium bismuth titanate - based piezoelectric ceramic material is prepared as in Example 1 of the invention with the publication number CN 116120054 A.

[0072] The Curie temperature ( T c ) of the calcium bismuth titanate - based piezoelectric ceramics prepared in Examples 1 - 6, the piezoelectric ceramic materials prepared in Comparative Examples 1 - 12, and the calcium bismuth titanate - based piezoelectric ceramic material prepared in Comparative Example 13, and the piezoelectric constant at room temperature ( d 33), resistivity (ρ), dielectric constant at room temperature, dielectric loss (tanδ) at room temperature, and electromechanical coupling coefficient at room temperature ( k p ) are shown in Table 4.

[0073] Table 4

[0074]

[0075] The XRD diffraction patterns of the calcium bismuth titanate-based piezoelectric ceramics prepared in Examples 1-6 are as Figure 1 shown, indicating that the calcium bismuth titanate-based piezoelectric ceramics prepared in Examples 1-6 all formed a single calcium bismuth titanate structure without generating a second phase. It shows that (NaCe) 5+ and (Co 1 / 2 Nb 1 / 2 ) 4+ have been successfully doped into CaBi4Ti4O 15 .

[0076] The SEM scanning electron microscope images of the calcium bismuth titanate-based piezoelectric ceramics prepared in Examples 2-5 are as Figure 2 shown. The grain boundaries of the calcium bismuth titanate-based piezoelectric ceramics prepared in Examples 2-5 are clearly visible and densely arranged, indicating that the calcium bismuth titanate-based piezoelectric ceramics prepared in Examples 2-5 have good density.

[0077] The variation of the dielectric loss of the calcium bismuth titanate-based piezoelectric ceramics prepared in Examples 1-6 with temperature is as Figure 3 shown ( Figure 3 in which the ordinate "Loss" represents the dielectric loss, and the temperature change range in the abscissa is: room temperature to 600 °C). In the range of room temperature to 600 °C, with the increase of temperature, the change trend of the dielectric loss is slow, indicating that the calcium bismuth titanate-based piezoelectric ceramics prepared in Examples 1-6 have excellent thermal stability and good piezoelectric properties.

[0078] The variation of the dielectric loss of the piezoelectric ceramic materials prepared in Comparative Examples 7-12 with temperature is as Figure 4 shown ( Figure 4 in which the ordinate "Loss" represents the dielectric loss, and the temperature change range in the abscissa is: room temperature to 600 °C). In the range of room temperature to 600 °C, with the increase of temperature, the change trend of the dielectric loss of the piezoelectric ceramic materials prepared in Comparative Examples 7-12 is larger than that of the calcium bismuth titanate-based piezoelectric ceramics prepared in Examples 1-6, indicating that the piezoelectric ceramic materials prepared in Comparative Examples 7-12 have poor thermal stability.

[0079] The variation of the dielectric constant of the calcium bismuth titanate-based piezoelectric ceramics prepared in Example 3 with temperature is as Figure 5As shown, an obvious mutation occurs at a temperature of 786°C. Before this temperature, the dielectric constant shows a slow upward trend with the increase in temperature. After reaching 786°C, the dielectric constant increases sharply with the increase in temperature. This mutation point is its Curie temperature point. The Curie temperature of the calcium bismuth titanate-based piezoelectric ceramic prepared in Example 3 is as high as 786°C.

[0080] The variation of the piezoelectric constant of the calcium bismuth titanate-based piezoelectric ceramics prepared in Examples 1 to 6 with temperature is as Figure 6 shown. In the range of room temperature to 650°C, with the increase in temperature, the variation amplitude of the piezoelectric constant of the calcium bismuth titanate-based piezoelectric ceramics prepared in Examples 1 to 6 is small, having excellent thermal stability. And as Figure 6 can be seen, in the range of room temperature to 650°C, the change rate of the piezoelectric constant of the calcium bismuth titanate-based piezoelectric ceramic prepared in Example 3 (the best example) is 5.6%. The variation of the piezoelectric constant of the piezoelectric ceramic material prepared in Comparative Example 3 with temperature is as Figure 7 shown. As Figure 7 can be seen, although the piezoelectric constant of the piezoelectric ceramic material prepared in Comparative Example 3 is very high, its thermal stability is poor.

[0081] The variation of the piezoelectric constant of the piezoelectric ceramic materials prepared in Comparative Examples 7 to 12 with temperature is as Figure 8 shown. In the range of room temperature to 650°C, with the increase in temperature, the variation amplitude of the piezoelectric ceramic materials prepared in Comparative Examples 7 to 12 is large. Among them, the change rate of the piezoelectric constant of the piezoelectric ceramic material prepared in Comparative Example 9 in the range of room temperature to 650°C is 11.2%.

[0082] The variation of the resistivity of the calcium bismuth titanate-based piezoelectric ceramics prepared in Examples 1 to 6 with temperature is as Figure 9 shown. The resistivity of the calcium bismuth titanate-based piezoelectric ceramics prepared in Examples 1 to 6 all reaches 10 6 Ω·cm or more at 600°C, having a very high resistivity. Among them, the resistivity of the calcium bismuth titanate-based piezoelectric ceramic prepared in Example 3 is the highest, reaching 7.5×10 6 Ω·cm. And at 400°C, the resistivity of the calcium bismuth titanate-based piezoelectric ceramics prepared in Examples 1 to 6 is even as high as 10 8 Ω·cm or more.

[0083] The above makes an exemplary description of the present invention. It should be noted that without departing from the core of the present invention, any simple deformation, modification, or equivalent substitution that can be made by those skilled in the art without creative labor falls within the protection scope of the present invention.

Claims

1. A method for preparing calcium bismuth titanate-based piezoelectric ceramics, characterized in that: The following steps are involved: Step 1, mixing a Ca source, a Na source, a Ce source, a Bi source, a Ti source, a Co source, a Nb source and a Cr source to obtain a mixture, mixing the mixture evenly, and pre-sintering at 750-900° C. for 2-4 hours to obtain a pre-sintered material, wherein, by amount of substance, the ratio of Ca in the Ca source, Na in the Na source, Ce in the Ce source, Bi in the Bi source, Ti in the Ti source, Co in the Co source, Nb in the Nb source and Cr in the Cr source is (0.93-0.95): (0.02-0.03): (0.02-0.03): 4: (3.93-3.95): (0.025-0.035): (0.025-0.035): 0.02; Step 2, mixing the pre-sintered materials uniformly, granulating, vacuum packaging, and warm isostatic pressing to obtain a green column; Step 3, debinding the green column, and performing a first sintering at 1000-1300° C. to obtain a ceramic material, wherein the first sintering time is 3-5 hours; Step 4, coating the ceramic material with high-temperature silver paste, sintering for a second time, and polarizing with high voltage in silicone oil in sequence to obtain bismuth calcium titanate-based piezoelectric ceramics; In calcium bismuth titanate-based piezoelectric ceramics, A-site doping (NaCe) 5+ Composite ions, B-site doping (Co 1 / 2 Nb 1 / 2 ) 4+ Composite ions are modified by adding Cr2O3 on this basis.

2. The preparation method according to claim 1, characterized in that: In step 2, the granulation uses a binder, and the ratio of the binder to the pre-sintered material is (2-5):1 by weight.

3. The preparation method according to claim 1, characterized in that: In step 2, the vacuum packaging includes: column packaging at a pressure of 2-4 MPa.

4. The preparation method according to claim 1, characterized in that: In step 2, the pressure of the warm isostatic pressing is 30-50 MPa, the holding time of the warm isostatic pressing is 10-20 s, and the temperature of the warm isostatic pressing is 25-40°C.

5. The preparation method according to claim 1, characterized in that: In step 3, the temperature of the debinding treatment is 550-650° C., and the time of the debinding treatment is 0.5-2 h.

6. The preparation method according to claim 1, characterized in that: In step 4, the second sintering includes: keeping the temperature at 800-850° C. for 10-40 minutes in an air environment.

7. The preparation method according to claim 1, characterized in that: In step 4, the high voltage polarization in silicone oil includes: polarizing in silicone oil at 150-200° C. with a polarization field strength of 10-12 kV / mm for 30-40 minutes.

8. The preparation method according to claim 4, characterized in that: The pressure increase rate of the warm isostatic pressing is 2-3 MPa / s.

9. The bismuth calcium titanate-based piezoelectric ceramic obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the bismuth calcium titanate-based piezoelectric ceramic according to claim 9 in an acceleration sensor.

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