A bismuth calcium niobate-based bismuth layered structure ferroelectric piezoelectric ceramic and a preparation method thereof

Abstract

The application provides a bismuth calcium niobate-based bismuth layered structure ferroelectric piezoelectric ceramic and a preparation method thereof, and belongs to the technical field of piezoelectric ceramic materials. The chemical general formula of the ferroelectric piezoelectric ceramic material is: Ca (1‑x‑y‑z) (Li 0.5 Bi 0.4 Ce 0.1 ) x Sr y Ba z Bi2Nb2O9, wherein 0 <= x <= 0.4, 0 <= y <= 0.2, and 0 <= z <= 0.2. The bismuth calcium niobate-based bismuth layered structure piezoelectric ceramic material only adopts ions with different sizes to simultaneously perform A-site doping, and adopts a traditional solid-phase method, so that the doping method is simple and effective, the preparation cost is low, and batch production is possible. The bismuth calcium niobate-based bismuth layered structure piezoelectric ceramic material has excellent and stable comprehensive electrical properties under a high-temperature environment (> 500 DEG C): when x = 0.2, y = 0.1, and z = 0.1, the d33 of the sample is 23.8 pC / N, the d33 is 22.5 pC / N after annealing at 900 DEG C for 2h, which is still 94.5% of that at room temperature, the piezoelectricity is high, and the temperature stability is high; the bulk resistivity at 600 DEG C is 2.4*106 Omega*cm; the Curie temperature remains high, Tc = 917 DEG C, and the excellent and stable electrical properties have practical application values in the field of high-temperature piezoelectric devices.

Description

Technical Field

[0001] This invention belongs to the field of piezoelectric ceramic materials technology, specifically relating to a bismuth niobate calcium-based bismuth layered structure ferroelectric piezoelectric ceramic and its preparation method. Background Technology

[0002] Piezoelectric ceramics are functional ceramic materials capable of converting electrical energy and mechanical energy into each other. Under the action of an external electric field, the material will produce strain, while under the action of mechanical force, the positive and negative charge centers inside the material will undergo relative displacement, thereby generating opposite charges at the two poles of the material.

[0003] Today, the application scope of various piezoelectric devices is constantly expanding, and the application environment is gradually extending to high-temperature environments. For example, the demand for high-temperature piezoelectric devices is constantly increasing in aero-engines, gas turbines, geothermal energy development, geological exploration, and nuclear reactors. This leads to an urgent need for high-performance high-temperature piezoelectric materials.

[0004] Among various piezoelectric materials, considering factors such as usable temperature range, electrical properties, production cost, and fabrication process, modified bismuth layer-structured ferroelectrics (BLSFs) are the best choice for fabricating high-temperature piezoelectric devices. Therefore, developing high-performance BLSFs materials is crucial for fabricating high-performance high-temperature piezoelectric devices.

[0005] The unique properties of BLSFs are all determined by their crystal structure; the general formula of these compounds is (Bi₂O₂). 2+ (A m-1 B m O 3m+1 ) 2- It is composed of a perovskite-like layer and (Bi2O2). 2+ The layers are formed by alternating stacking along the c-axis, where A and B sites are ions with suitable radii and valence states for 12-coordinate and 6-coordinate ions, respectively, and m is the number of oxygen octahedral layers in the perovskite-like layer, taking an integer between 1 and 6. For BLSFs, A-site ion doping has a more significant modification effect than B-site ion doping. This is because B-site ions are smaller and located at the body center of the perovskite octahedron, while A-site ions are larger. A-site doping significantly affects the crystal structure of the material, thus having a greater impact on the Curie temperature and electrical properties.

[0006] T of CaBi2Nb2O9(CBN) piezoelectric ceramics C With a Curie temperature of approximately 941℃, it is the highest among BLSFs and has significant application prospects in the field of high-temperature (>500℃) piezoelectric materials. However, the overall electrical properties of doped and modified CBN are still relatively poor, mainly in the following aspects: 1) poor piezoelectricity, d33 ≤20pC / N; 2) Poor piezoelectric temperature stability, piezoelectricity decreases significantly with increasing temperature; 3) Low high-temperature resistivity, r=10 5 Ω·cm (@500℃). These shortcomings greatly limit its practical application in high-temperature fields.

[0007] Patent document CN 116102345 A discloses a bismuth layered piezoelectric ceramic material with the general formula: Ca 0.86 (LiCe) 0.07 Bi4Ti 3.99 Zn 0.01 O 15 +x wt% Bi₂O₃ +y wt% Li₂CO₃, where x is 0.05–0.4 and y is 0.002–0.005. However, this piezoelectric ceramic material exhibits poor piezoelectricity, d 33 =19pC / N, and its Curie temperature is relatively low, Tc=810℃.

[0008] Patent document CN 104529447 B discloses a bismuth layered composite piezoelectric ceramic material with the general formula: [Ca 1-x Me x Bi2Nb 2-2y Me' 2y O9] 1-z -[Bi 3-a Me a (TiNb) 1-b Me' 2b O9] z ; 0 < x ≤ 0.05, 0 < y ≤ 0.05, 0 < a ≤ 0.05, 0 < b ≤ 0.05, 0.2 ≤ z ≤ 0.8, however, the piezoelectric properties of this bismuth layered piezoelectric ceramic material are: d 33 =19pC / N, Tc=810℃, its piezoelectricity and Curie temperature are both low.

[0009] Therefore, there is an urgent need to provide a bismuth layered piezoelectric ceramic material with excellent piezoelectric properties, high piezoelectric temperature stability, high high-temperature resistivity, and high Curie temperature. Summary of the Invention

[0010] The present invention aims to solve the aforementioned technical problems by providing a bismuth calcium niobate-based bismuth layered piezoelectric ceramic and its preparation method. The technical objective of this invention is to address the problems of poor piezoelectric performance, poor piezoelectric temperature stability, low high-temperature resistivity, and low Curie temperature found in existing bismuth layered piezoelectric ceramics.

[0011] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0012] This invention first provides a bismuth niobate calcium-based bismuth layered ferroelectric ceramic material, the chemical formula of which is: Ca (1-x-y-z) (Li 0.5 Bi 0.4 Ce 0.1 ) x Sr y Ba z Bi2Nb2O9, where 0≤x≤0.4, 0≤y≤0.2, 0≤z≤0.2.

[0013] This invention utilizes (Li) of different sizes 0.5 Bi 0.4 Ce 0.1 ) 2+ 、Sr 2+ Ba 2+ For CBN piezoelectric ceramics, the A-site Ca 2+ Simultaneous isovalent substitution (ion size: R) (Li0.5Bi0.4Ce0.1) 2+ <R Ca 2+ <R Sr 2+ <R Ba 2+ This process causes distortion in the crystal structure, significantly improving the electrical properties of CBN-based piezoelectric ceramics. This overcomes the technical problems of existing piezoelectric ceramic materials, such as poor piezoelectricity at high temperatures, poor temperature stability of piezoelectric properties, and low resistivity. This invention yields a CBN-based bismuth layered piezoelectric ceramic material with stable comprehensive electrical properties at high temperatures.

[0014] Furthermore, the ferroelectric ceramic material includes Ca. 0.6 Sr 0.2 Ba 0.2 Bi2Nb2O9, Ca 0.6 (Li 0.5 Bi 0.4 Ce 0.1 ) 0.1 Sr 0.15 Ba 0.15 Bi2Nb2O9, Ca 0.6 (Li 0.5 Bi 0.4 Ce 0.1 ) 0.2 Sr 0.1 Ba 0.1 Bi2Nb2O9, Ca 0.6 (Li 0.5 Bi 0.4 Ce 0.1 ) 0.3 Sr 0.05Ba 0.05 Bi2Nb2O9 or Ca 0.6 (Li 0.5 Bi 0.4 Ce 0.1 ) 0.4 Bi2Nb2O9.

[0015] Furthermore, the Curie temperature of the ferroelectric piezoelectric ceramic material is 908–931°C, the piezoelectric constant is 17.5–23.8 pC / N, the relative permittivity is 100–115, and the dielectric loss is 0.1%.

[0016] The second objective of this invention is to provide a method for preparing the bismuth niobate calcium-based bismuth layered ferroelectric ceramic material as described above, comprising the following steps:

[0017] (1) Ingredients: Calculate and weigh the corresponding raw materials according to the stoichiometric ratio in the general formula. The raw materials include calcium carbonate, bismuth oxide, niobium pentoxide, lithium carbonate, cerium oxide, strontium carbonate and barium carbonate.

[0018] (2) Mixing and ball milling: The weighed raw materials are placed in a ball milling jar, mixed with ball milling media and anhydrous ethanol, and ball milled to obtain primary ball milling material;

[0019] (3) Pre-calcination: The primary ball milling material is dried, ground and sieved, and then pre-calcined to obtain pre-calcined powder.

[0020] (4) Secondary ball milling: The pre-calcined powder is placed in a ball milling jar, mixed with ball milling media and anhydrous ethanol, and ball milled to obtain secondary ball milling material;

[0021] (5) Granulation and tableting: After drying the secondary ball milling material, grind and sieve it, add a binder and grind and granulate it to obtain granulated powder, and press the granulated powder into shape.

[0022] (6) Debinding: Debinding the pressed ceramic sheet to obtain a ceramic blank;

[0023] (7) Sintering: The ceramic blank is sintered to obtain sintered ceramic sheets;

[0024] (8) Upper electrode: The upper electrode is applied after polishing both sides of the sintered ceramic sheet;

[0025] (9) Polarization: Apply voltage to the ceramic sheet after the upper electrode to polarize it, and obtain the bismuth niobate calcium-based bismuth layered structure ferroelectric ceramic material.

[0026] Furthermore, the ball milling media in steps (2) and (4) are zirconia balls, and the weight ratio of zirconia balls, total raw materials and anhydrous ethanol is controlled to be 3:1:1.

[0027] Furthermore, the ball milling time in step (2) is 10-16 hours, and the ball milling time in step (4) is 18-24 hours.

[0028] Furthermore, the pre-firing temperature in step (3) is 850-900°C, and the pre-firing time is 2-5 hours.

[0029] Furthermore, the adhesive mentioned in step (5) is polyvinyl alcohol, which is prepared into a solution with a mass concentration of 8%, and the mass of the polyvinyl alcohol solution is 8 to 10% of the total mass of the raw materials.

[0030] Preferably, the sieve mesh size is 60 mesh; the pressing pressure is 10 MPa, the pressing thickness is 0.5 mm, and the tablet diameter is 10 mm.

[0031] Furthermore, the conditions for the glue removal process in step (6) are: a heating rate of 1℃ / min, a temperature of 650~750℃, and a holding time of 3~4 hours.

[0032] Furthermore, the sintering process described in step (7) is as follows: first, the temperature is raised to 1000℃ at a rate of 10℃ / min, and then raised to 1100-1200℃ at a rate of 3℃ / min, and held for 2-4 hours.

[0033] Furthermore, the operation of the upper electrode in step (8) is as follows: printing silver or platinum electrodes on a sintered ceramic sheet polished on both sides, controlling the silver firing conditions to be kept at 650°C for 10-15 minutes, and controlling the platinum firing conditions to be kept at 1000°C for 15-20 minutes.

[0034] Preferably, in step (9), silicone oil is added during polarization and the temperature of the silicone oil is controlled at 180-200°C, the polarization electric field is 8-15kV / mm, and the holding time is 15-30 minutes.

[0035] The beneficial effects of this invention are as follows:

[0036] 1. The bismuth niobate-calcium bismuth layered piezoelectric ceramic material provided by the present invention uses only ions of different sizes to simultaneously perform A-site doping, and adopts the traditional solid-state method. The doping method is simple and effective, the preparation cost is low, and it can be mass-produced.

[0037] 2. The bismuth niobate-calcium bismuth layered piezoelectric ceramic material provided by this invention possesses excellent and stable comprehensive electrical properties under high-temperature conditions (>500℃): when x=0.2, y=0.1, z=0.1, the sample's d 33 =23.8pC / N, after annealing at 900℃ for 2 hours, d 33=22.5pC / N, still 94.5% of the value at room temperature, exhibiting high piezoelectricity and temperature stability; volume resistivity at 600℃ = 2.4×10⁻⁶. 6 The temperature remains high at Ω·cm, with a Curie temperature of Tc = 917℃. Its excellent and stable electrical properties have practical application value in the field of high-temperature piezoelectric devices. Attached Figure Description

[0038] Figure 1 The annealing curves are those of the bismuth niobate calcium-based piezoelectric ceramics prepared in Examples 1-5 of this invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described in detail below with reference to embodiments. It should be noted that the following embodiments are for explanation and illustration only and are not intended to limit the invention. Non-essential improvements and adjustments made by those skilled in the art based on the above description are still within the scope of protection of this invention.

[0040] Example 1

[0041] Ca was prepared by solid-state reaction method 0.6 Sr 0.2 Ba 0.2 Bi2Nb2O9 piezoelectric ceramic (abbreviated as 1#), where x=0, y=0.2, z=0.2.

[0042] The preparation method of the above-mentioned piezoelectric ceramic 1# includes the following steps:

[0043] S1. Ingredients: Calculate and weigh various raw materials according to the stoichiometric ratio of ceramics. The raw materials include (the values ​​in parentheses after the raw materials refer to the content of the raw materials) calcium carbonate CaCO3 (99.99%), bismuth oxide Bi2O3 (99.99%), niobium pentoxide Nb2O5 (99.99%), strontium carbonate SrCO3 (99.9%), and barium carbonate BaCO3 (99.9%).

[0044] S2. Mixing and ball milling: Place the weighed raw materials into a ball mill jar, use zirconia balls as the ball milling medium and anhydrous ethanol as the solvent, and rotate the planetary ball mill for 12 hours at a speed of 280 rpm.

[0045] S3. Pre-firing: The above-mentioned ball milling material is dried by baking with a baking lamp for 2 hours, then placed in a crucible, compacted, covered with a crucible lid, and placed in a furnace, and kept at 850℃ for 2 hours.

[0046] S4. Secondary ball milling: The above pre-sintered powder is placed in a ball mill jar, and zirconia balls are used as the ball milling medium and anhydrous ethanol is used as the solvent. The mixture is milled in a planetary ball mill for 24 hours at a speed of 280 rpm.

[0047] S5. Granulation and tableting: After drying the above-mentioned secondary ball milling material by baking with a baking lamp for 2 hours, grind it thoroughly, add 10% of the powder mass of polyvinyl alcohol (PVA) solution, grind and granulate, and pass through a 60-mesh sieve to obtain granulated powder. Press the granulated powder into small round tablets with a thickness of 0.5 mm and a diameter of 10 mm using a pressing mold under a pressure of 10 MPa, and press a total of 10 tablets.

[0048] S6. Debinding: Place the pressed round sheet on the firing plate and put it into the debinding furnace. Heat it to 750℃ at a heating rate of 1℃ / min and keep it at that temperature for 2 hours.

[0049] S7. Sintering: The above ceramic green body is stacked on a sintering plate with granulation powder, the crucible is inverted and sealed, and then placed in a sintering furnace and held at 1115℃ for 2 hours.

[0050] S8. Upper electrode: Polish both sides of the above sintered ceramic sheet, print silver paste, and heat at 650℃ for 15 minutes to burn silver.

[0051] S9. Polarization: Grind off the silver paste adhering to the edge of the silver ceramic sheet, place the ceramic sheet in silicone oil at 180℃, and hold it under an electric field of 11kV / mm for 30 minutes to obtain the Ca. 0.6 Sr 0.2 Ba 0.2 Bi2Nb2O9 is a bismuth layered piezoelectric ceramic material.

[0052] Example 2

[0053] Ca was prepared by solid-state reaction method 0.6 (Li 0.5 Bi 0.4 Ce 0.1 ) 0.1 Sr 0.15 Ba 0.15 Bi2Nb2O9 piezoelectric ceramic (abbreviated as 2#), where x = 0.1, y = 0.15, z = 0.15.

[0054] The preparation method of the above-mentioned piezoelectric ceramic #2 includes the following steps:

[0055] S1. Ingredients: Calculate and weigh various raw materials according to the above stoichiometric ratios, including calcium carbonate CaCO3 (99.99%), bismuth oxide Bi2O3 (99.99%), niobium pentoxide Nb2O5 (99.99%), lithium carbonate Li2CO3 (99.8%), cerium oxide CeO2 (99%), strontium carbonate SrCO3 (99.9%), and barium carbonate BaCO3 (99.9%).

[0056] S2. Mixing and ball milling: Place the weighed raw materials into a ball mill jar, use zirconia balls as the ball milling medium and anhydrous ethanol as the solvent, and rotate the planetary ball mill for 12 hours at a speed of 280 rpm.

[0057] S3. Pre-firing: The above-mentioned primary ball milling material is dried by baking with a baking lamp for 2 hours, then placed in a crucible, compacted, covered with a crucible lid, and placed in a furnace, and kept at 850℃ for 2 hours.

[0058] S4. Secondary ball milling: The above pre-sintered powder is placed in a ball mill jar, still using zirconia balls as the ball milling medium and anhydrous ethanol as the solvent, and rotated in a planetary ball mill for 24 hours at a speed of 280 rpm.

[0059] S5. Granulation and tableting: After drying the above-mentioned secondary ball milling material by baking with a baking lamp for 2 hours, grind it thoroughly, add 10% of the powder mass of PVA solution, grind and granulate, and pass through a 60-mesh sieve to obtain granulated powder. Press the granulated powder into small round tablets with a thickness of 0.5 mm and a diameter of 10 mm using a pressing mold under a pressure of 10 MPa, for a total of 8 tablets.

[0060] S6. Debinding: Place the pressed round sheet on the firing plate and put it into the debinding furnace. Heat it to 750℃ at a heating rate of 1℃ / min and keep it at that temperature for 2 hours.

[0061] S7. Sintering: The above ceramic green body is stacked on a sintering plate with granulation powder, the crucible is inverted and sealed, and then placed in a sintering furnace and held at 1110℃ for 2 hours.

[0062] S8. Upper electrode: Polish both sides of the above sintered ceramic sheet, print silver paste, and heat at 650℃ for 15 minutes to burn silver.

[0063] S9. Polarization: Grind off the silver paste adhering to the edge of the silver ceramic sheet, place the ceramic sheet in silicone oil at 180℃, and hold it under an electric field of 12.5kV / mm for 30 minutes to obtain the Ca. 0.6 (Li 0.5 Bi 0.4 Ce 0.1 ) 0.1 Sr 0.15 Ba 0.15 Bi2Nb2O9 is a bismuth layered piezoelectric ceramic material.

[0064] Example 3

[0065] Ca was prepared by solid-state reaction method 0.6 (Li 0.5 Bi 0.4 Ce 0.1 ) 0.2 Sr 0.1 Ba 0.1Bi2Nb2O9 piezoelectric ceramic (abbreviated as 3#), where x=0.2, y=0.1, z=0.1.

[0066] The preparation method of the above-mentioned piezoelectric ceramic #3 includes the following steps:

[0067] S1. Ingredients: Calculate and weigh various raw materials according to the above stoichiometric ratios, including calcium carbonate CaCO3 (99.99%), bismuth oxide Bi2O3 (99.99%), niobium pentoxide Nb2O5 (99.99%), lithium carbonate Li2CO3 (99.8%), cerium oxide CeO2 (99%), strontium carbonate SrCO3 (99.9%), and barium carbonate BaCO3 (99.9%).

[0068] S2. Mixing and ball milling: Place the weighed raw materials into a ball mill jar, use zirconia balls as the ball milling medium and anhydrous ethanol as the solvent, and rotate the planetary ball mill for 12 hours at a speed of 280 rpm.

[0069] S3. Pre-firing: The above-mentioned primary ball milling material is dried by baking with a baking lamp for 2 hours, then placed in a crucible, compacted, covered with a crucible lid, and placed in a furnace, and kept at 850℃ for 2 hours.

[0070] S4. Secondary ball milling: The above pre-sintered powder is placed in a ball mill jar, still using zirconia balls as the ball milling medium and anhydrous ethanol as the solvent, and rotated in a planetary ball mill for 24 hours at a speed of 280 rpm.

[0071] S5. Granulation and tableting: After drying the above-mentioned secondary ball milling material by baking with a baking lamp for 2 hours, grind it thoroughly, add 10% of the powder mass of PVA solution, grind and granulate, and pass through a 60-mesh sieve to obtain granulated powder. Press the granulated powder into small round tablets with a thickness of 0.5 mm and a diameter of 10 mm using a pressing mold under a pressure of 10 MPa, for a total of 8 tablets.

[0072] S6. Debinding: Place the pressed round sheet on the firing plate and put it into the debinding furnace. Heat it to 750℃ at a heating rate of 1℃ / min and keep it at that temperature for 2 hours.

[0073] S7. Sintering: The ceramic green body is stacked on a sintering plate with granulated powder in between, the crucible is inverted and sealed, and then placed in a sintering furnace and kept at 1110℃ for 2 hours.

[0074] S8. Upper electrode: After polishing both sides of the sintered ceramic sheet, silver paste is printed on it, and silver is burned at 650°C for 15 minutes.

[0075] S9. Polarization: Grind off the silver paste adhering to the edge of the silver ceramic sheet, place the ceramic sheet in silicone oil at 180℃, and hold it under an electric field of 13kV / mm for 30 minutes to obtain the Ca. 0.6 (Li 0.5 Bi0.4 Ce 0.1 ) 0.2 Sr 0.1 Ba 0.1 Bi2Nb2O9 is a bismuth layered piezoelectric ceramic material.

[0076] Example 4

[0077] Ca was prepared by solid-state reaction method 0.6 (Li 0.5 Bi 0.4 Ce 0.1 ) 0.3 Sr 0.05 Ba 0.05 Bi2Nb2O9 piezoelectric ceramic (abbreviated as 4#), where x=0.3, y=0.05, z=0.05.

[0078] The preparation method of the above-mentioned piezoelectric ceramic #4 includes the following steps:

[0079] S1. Ingredients: Calculate and weigh various raw materials according to the above stoichiometric ratios, including calcium carbonate CaCO3 (99.99%), bismuth oxide Bi2O3 (99.99%), niobium pentoxide Nb2O5 (99.99%), lithium carbonate Li2CO3 (99.8%), cerium oxide CeO2 (99%), strontium carbonate SrCO3 (99.9%), and barium carbonate BaCO3 (99.9%).

[0080] S2. Mixing and ball milling: Place the weighed raw materials into a ball mill jar, use zirconia balls as the ball milling medium and anhydrous ethanol as the solvent, and rotate the planetary ball mill for 12 hours at a speed of 280 rpm.

[0081] S3. Pre-firing: The above-mentioned primary ball milling material is dried by baking with a baking lamp for 2 hours, then placed in a crucible, compacted, covered with a crucible lid, and placed in a furnace, and kept at 850℃ for 2 hours.

[0082] S4. Secondary ball milling: The pre-sintered powder is placed in a ball milling jar, still using zirconia balls as the ball milling medium and anhydrous ethanol as the solvent, and rotated in a planetary ball mill for 24 hours at a speed of 280 rpm.

[0083] S5. Granulation and tableting: The secondary ball milling material is dried by baking with a baking lamp for 2 hours and then fully ground. 10% of the powder mass of PVA solution is added, and the mixture is ground and granulated and passed through a 60-mesh sieve to obtain granulated powder. The granulated powder is pressed into small round tablets with a thickness of 0.5 mm and a diameter of 10 mm using a pressing mold under a pressure of 10 MPa, for a total of 8 tablets.

[0084] S6. Debinding: Place the pressed round sheet on the firing plate and put it into the debinding furnace. Heat it to 750℃ at a heating rate of 1℃ / min and keep it at that temperature for 2 hours.

[0085] S7. Sintering: The ceramic green body is stacked on a sintering plate with granulated powder in between, the crucible is inverted and sealed, and then placed in a sintering furnace and kept at 1110℃ for 2 hours.

[0086] S8. Upper electrode: After polishing both sides of the sintered ceramic sheet, silver paste is printed on it, and silver is burned at 650°C for 15 minutes.

[0087] S9. Polarization: Grind off the silver paste adhering to the edge of the silver ceramic sheet, place the ceramic sheet in silicone oil at 180℃, and maintain the voltage for 30 minutes under an electric field of 13.5kV / mm to obtain the Ca. 0.6 (Li 0.5 Bi 0.4 Ce 0.1 ) 0.3 Sr 0.05 Ba 0.05 Bi2Nb2O9 is a bismuth layered piezoelectric ceramic material.

[0088] Example 5

[0089] Ca was prepared by solid-state reaction method 0.6 (Li 0.5 Bi 0.4 Ce 0.1 ) 0.4 Bi2Nb2O9 piezoelectric ceramic (abbreviated as 5#), where x=0.4, y=0, z=0.

[0090] The preparation method of the above-mentioned piezoelectric ceramic #5 includes the following steps:

[0091] S1. Ingredients: Calculate and weigh various raw materials according to the above stoichiometric ratios, including calcium carbonate CaCO3 (99.99%), bismuth oxide Bi2O3 (99.99%), niobium pentoxide Nb2O5 (99.99%), lithium carbonate Li2CO3 (99.8%), and cerium oxide CeO2 (99%).

[0092] S2. Mixing and ball milling: Place the weighed raw materials into a ball mill jar, use zirconia balls as the ball milling medium and anhydrous ethanol as the solvent, and rotate the planetary ball mill for 12 hours at a speed of 280 rpm.

[0093] S3. Pre-firing: The primary ball milling material is dried by baking with a baking lamp for 2 hours, then placed in a crucible, compacted, and covered with a crucible lid and placed in a furnace, and kept at 850°C for 2 hours.

[0094] S4. Secondary ball milling: The pre-sintered powder is placed in a ball milling jar, still using zirconia balls as the ball milling medium and anhydrous ethanol as the solvent, and rotated in a planetary ball mill for 24 hours at a speed of 280 rpm.

[0095] S5. Granulation and tableting: The secondary ball milling material is dried by baking with a baking lamp for 2 hours and then fully ground. 10% of the powder mass of PVA solution is added, and the mixture is ground and granulated and passed through a 60-mesh sieve to obtain granulated powder. The granulated powder is pressed into small round tablets with a thickness of 0.5 mm and a diameter of 10 mm using a pressing mold under a pressure of 10 MPa, for a total of 8 tablets.

[0096] S6. Debinding: Place the pressed round sheet on the firing plate and put it into the debinding furnace. Heat it to 750℃ at a heating rate of 1℃ / min and keep it at that temperature for 2 hours.

[0097] S7. Sintering: The ceramic green body is stacked on a sintering plate with granulated powder in between, the crucible is inverted and sealed, and then placed in a sintering furnace and kept at 1105℃ for 2 hours.

[0098] S8. Upper electrode: After polishing both sides of the sintered ceramic sheet, silver paste is printed on it, and silver is burned at 650°C for 15 minutes.

[0099] S9. Polarization: Grind off the silver paste adhering to the edge of the silver ceramic sheet, place the ceramic sheet in silicone oil at 180℃, and maintain the voltage for 30 minutes under an electric field of 13.5kV / mm to obtain the Ca. 0.6 (Li 0.5 Bi 0.4 Ce 0.1 ) 0.4 Bi2Nb2O9 is a bismuth layered piezoelectric ceramic material.

[0100] Experimental Example

[0101] This experimental example investigated the simultaneous substitution of A-site Ca by ions of different sizes. 2+ The comprehensive electrical properties of CBN piezoelectric ceramics are shown in Table 1. Table 1 lists the main performance parameters of the five ceramics prepared by solid-state method in Examples 1-5. The results show that with the increase of small-sized ions (Li... 0.5 Bi 0.4 Ce 0.1 ) 2+ Increased doping concentration and larger ion size (Sr) 2+ Ba 2+ As the doping concentration decreases, the piezoelectric constant of CBN ceramics first increases and then decreases, with ceramic #4 exhibiting the highest piezoelectric constant. 33 =23.8 pC / N, indicating that small-sized ions substitute for Ca at the A site. 2+ It can more effectively improve the piezoelectric properties of CBN ceramics, but the Curie temperature (Tc) is reduced.

[0102] The ceramics prepared in this experiment all exhibit high high-temperature resistivity; at 600℃, the bulk resistivity (r) is 10. 6The piezoelectric properties are on the order of Ω·cm, which is extremely advantageous for their application in high-temperature environments. Since high-temperature piezoelectric devices operate for extended periods in environments exceeding 500°C, the excellent high-temperature temperature stability of their piezoelectric components is particularly important. Figure 1 The annealing curves for ceramics prepared by the solid-state method in Examples 1-5 are shown. Each group of ceramics was annealed in a temperature range from room temperature to 1000℃, and held at each temperature for 2 hours. After annealing at 900℃ for 2 hours, ceramic #4 still had a piezoelectricity of 22.5 pC / N, which was 94.5% of that at room temperature, indicating high piezoelectricity and temperature stability.

[0103] To further evaluate the performance of the ceramic material in this invention, it is compared with the performance of bismuth layered piezoelectric ceramic materials provided by other inventions. Taking sample #4 as an example, see Table 2 below (all materials in the table are prepared using the traditional solid-state method). Since other piezoelectric ceramic materials have low Curie temperatures, they are generally not applicable to high-temperature environments above 500℃. Therefore, this invention only compares the performance with that of bismuth layered piezoelectric ceramic materials.

[0104] The bismuth layered piezoelectric ceramic provided in this invention has a Curie temperature of 917℃, a piezoelectric constant of 23.8 pC / N, and a piezoelectric constant of 22.5 pC / N after annealing at 900℃ for 2 hours, which is still 94.5% of the room temperature value. Its high-temperature resistivity at 600℃ is 6.7 x 10⁻⁶. 6 Ω·cm. Comparison revealed that while other bismuth layered piezoelectric ceramics possess high Curie temperatures and high-temperature resistivity, their piezoelectricity is poor; conversely, while possessing high piezoelectricity and temperature stability, their Curie temperatures are low. This directly results in these materials failing to meet the basic performance requirements of high-temperature piezoelectric devices. The piezoelectric ceramic material provided by this invention possesses high Curie temperatures and high-temperature resistivity, as well as high piezoelectricity and piezoelectric temperature stability. Its excellent comprehensive electrical properties ensure stable operation of piezoelectric devices in high-temperature environments (>500℃), which is of paramount practical significance for the fabrication of high-performance high-temperature piezoelectric devices.

[0105] Table 1. Main performance parameters of ceramics prepared by solid-state method in Examples 1-5

[0106]

[0107] Table 2 Performance of various bismuth-doped layered piezoelectric ceramics

[0108]

[0109]

Claims

1. A method for producing a bismuth calcium niobate-based bismuth layer-structured ferroelectric piezoelectric ceramic material, characterized by, The ferroelectric piezoelectric ceramic material has a chemical formula as follows: Ca 0.6 Sr 0.2 Ba 0.2 Bi2Nb2O9, Ca 0.6 (Li 0.5 Bi 0.4 Ce 0.1 ) 0.1 Sr 0.15 Ba 0.15 Bi2Nb2O9, Ca 0.6 (Li 0.5 Bi 0.4 Ce 0.1 ) 0.2 Sr 0.1 Ba 0.1 Bi2Nb2O9 or Ca 0.6 (Li 0.5 Bi 0.4 Ce 0.1 ) 0.3 Sr 0.05 Ba 0.05 Bi2Nb2O9; The preparation method comprises the following steps: (1) batching: the corresponding raw materials are calculated and weighed according to the stoichiometric ratio in the chemical formula, and the raw materials include calcium carbonate, bismuth oxide, niobium pentoxide, lithium carbonate, cerium oxide, strontium carbonate and barium carbonate; (2) mixing and ball milling: the weighed raw materials are put into a ball mill tank, mixed with ball milling medium and anhydrous ethanol, the ball milling medium is zirconium oxide balls, and the weight ratio of zirconium oxide balls, raw materials and anhydrous ethanol is controlled to be 3:1:1, to obtain primary ball milling materials; (3) pre-sintering: the primary ball milling materials are dried, ground and sieved, pre-sintering is performed, the pre-sintering temperature is 850-900 DEG C, the pre-sintering time is 2-5 hours, and pre-sintered powder is obtained; (4) secondary ball milling: the pre-sintered powder is put into a ball mill tank, mixed with ball milling medium and anhydrous ethanol, the ball milling medium is zirconium oxide balls, and the weight ratio of zirconium oxide balls, raw materials and anhydrous ethanol is controlled to be 3:1:1, to obtain secondary ball milling materials; (5) granulation and tabletting: the secondary ball milling materials are dried, ground and sieved, a binder is added for grinding and granulation, granulated powder is obtained, and the granulated powder is pressed into shape; (6) glue removal: the ceramic sheet pressed into shape is subjected to glue removal treatment, and a ceramic body is obtained; (7) sintering: the ceramic body is sintered, and the sintering process is as follows: first, the temperature is raised to 1000 DEG C at a rate of 10 DEG C / min, then the temperature is raised to 1100-1200 DEG C at a rate of 3 DEG C / min, and the temperature is kept for 2-4 hours, to obtain a sintered ceramic sheet; (8) electrode application: the sintered ceramic sheet is polished on both sides, and an electrode is applied, the operation of applying the electrode is as follows: a silver electrode or a platinum electrode is printed on the sintered ceramic sheet polished on both sides, the silver burning condition is controlled to be 650 DEG C for 10-15 minutes, and the platinum burning condition is controlled to be 1000 DEG C for 15-20 minutes; (9) polarization: the ceramic sheet after electrode application is subjected to polarization by applying voltage, and the bismuth calcium niobate-based bismuth layered structure ferroelectric piezoelectric ceramic material is obtained.

2. The production method according to claim 1, characterized by, In step (2), the ball milling time is 10-16 hours, and in step (4), the ball milling time is 18-24 hours.

3. The production method according to claim 1, characterized by, In step (5), the binder is polyvinyl alcohol, the polyvinyl alcohol is prepared into a solution with a mass concentration of 8%, and the mass of the polyvinyl alcohol solution is 8-10% of the total mass of the raw materials.

4. The production method according to claim 1, characterized by, In step (5), the sieving mesh size is 60 mesh, the pressure for pressing into shape is 10 MPa, the pressing thickness is 0.5 mm, and the tablet diameter is 10 mm.

5. The preparation method according to claim 1, characterized in that, In step (6), the glue removal treatment conditions are as follows: the temperature rising rate is 1 DEG C / min, the temperature is raised to 650-750 DEG C, and the temperature is kept for 3-4 hours.

6. The method of claim 1, wherein, In step (9), silicon oil is added during polarization, the silicon oil temperature is controlled to be 180-200 DEG C, the polarization electric field is 8-15 kV / mm, and the pressure keeping time is 15-30 minutes.

7. The bismuth calcium niobate-based bismuth layer-structured ferroelectric piezoelectric ceramic material produced by the method according to any one of claims 1 to 6, characterized in that The ferroelectric piezoelectric ceramic material has a Curie temperature of 908-931 DEG C, a piezoelectric constant of 17.5-23.8 pC / N, a relative dielectric constant of 100-115, and a dielectric loss of 0.1%.

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