Cd / Sm / Ce / Zn / Sb / Sn / Mo doped Bi3TiNbO9 high-temperature piezoelectric ceramic material and preparation method thereof

Abstract

The invention discloses a Cd / Sm / Ce / Zn / Sb / Sn / Mo doped Bi3TiNbO9 high-temperature piezoelectric ceramic material and a preparation method thereof, Bi < 3 + > ions at the A site of the Bi3TiNbO9 ceramic material are doped and substituted by adopting composite high-valence ions [Cd0. 15Sm0. 15Ce0. 7] 3.55 < + > consisting of Cd < 2 + >, Sm < 3 + > and Ce < 4 + >, Ti < 4 + > and Nb < 5 + > ions at the B site are doped and substituted by adopting composite high-valence ions [Zn0. 25Sb0. 75] 4.25 < + > and [Sn0. 35Mo < 0.65 >] 5.3 < + > consisting of Zn < 2 + >, Sb < 5 + >, Sn < 4 + > and Mo < 6 + The invention provides a novel environment-friendly piezoelectric ceramic material with excellent comprehensive electrical properties, and the material has good high-temperature stability and wide application prospects in the high-temperature field. The preparation method adopts an advanced ceramic preparation process, has the advantages of low firing temperature, low preparation cost, simple process, easiness in operation and easiness in control of influence factors, is suitable for large-scale industrial production, and is beneficial to popularization and application.

Description

Technical Field

[0001] The present invention relates to the technical field of piezoelectric ceramic materials, and in particular to a doped bismuth layered structure bismuth niobate titanate high-temperature piezoelectric ceramic material and a preparation method thereof. Background Art

[0002] At present, the most widely used piezoelectric ceramic material is mainly lead zirconate titanate piezoelectric ceramics, but this type of piezoelectric ceramics contains lead, which causes harm to the environment and human body during production, use and waste disposal; and the Curie temperature of this type of piezoelectric ceramics is generally below 400℃. Due to the existence of the depolarization phenomenon of piezoelectric materials, piezoelectric materials cannot work normally above the Curie temperature. With the rapid development of aerospace, geological exploration and other work and in line with the needs of sustainable development of human society, it is necessary to seek an environmentally friendly piezoelectric material with high Curie temperature and excellent piezoelectric performance.

[0003] Bismuth layered ceramics have the characteristics of high Curie temperature, low dielectric loss, obvious anisotropy of electromechanical coupling coefficient, high resistivity, no pollution, low leakage current, excellent ferroelectric properties, etc., and are candidate materials suitable for high temperature environments. Bismuth layered ceramic materials are composed of (Bi2O2) 2+ The layers and perovskite-like structure lattice layers are alternately stacked, and its chemical formula is (Bi2O2) 2+ (A m-1 B m O 3m+1 ) 2- Among them, Bi3TiNbO9 (BTN) is a typical bismuth layered structure ferroelectric material, A is a 12-coordinated Bi 3+ , B is 6-coordinated Ti 4+ and Nb 5+ , m = 2, fluorite structure (Bi2O2) 2+ Layers and perovskite-like structures (BiTiNbO7) 2- The material has a very high Curie temperature (T C ≈914℃), good thermal stability and fatigue resistance, but the piezoelectric constant is very low (d 33 ≈4pC / N). Therefore, how to maintain a high Curie temperature while improving the piezoelectric activity and obtaining BTN piezoelectric ceramic materials with excellent comprehensive electrical properties has become an important research topic in the field of high-temperature piezoelectric ceramic materials. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a Cd / Sm / Ce / Zn / Sb / Sn / Mo doped Bi3TiNbO9 high temperature piezoelectric ceramic material. 3+ ions, using Cd with 12 coordination2+ 、Sm 3+ 、Ce 4+ Composition of complex high-valent ions [Cd 0.15 Sm 0.15 Ce 0.7 ] 3.55+ Doping substitution is performed for Ti at the B position 4+ , Nb 5+ ions, using Zn with 6 coordination 2+ , Sb 5+ Sn 4+ 、Mo 6+ Composition of complex high-valent ions [Zn 0.25 Sb 0.75 ] 4.25+ 、[Sn 0.35 Mo 0.65 ] 5.3+ It is doped and substituted so that through the above-mentioned composite doping modification, its piezoelectric properties and high-temperature resistivity are improved while maintaining a high Curie temperature, thereby providing a new type of piezoelectric ceramic material with excellent comprehensive electrical properties and environmental friendliness. Another object of the present invention is to provide a method for preparing the above-mentioned Cd / Sm / Ce / Zn / Sb / Sn / Mo doped Bi3TiNbO9 high-temperature piezoelectric ceramic material.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] The present invention provides a Cd / Sm / Ce / Zn / Sb / Sn / Mo doped Bi3TiNbO9 high temperature piezoelectric ceramic material with 12-coordinated Cd 2+ 、Sm 3+ 、Ce 4+ The complex high-valent ions [Cd 0.15 Sm 0.15 Ce 0.7 ] 3.55+ Doping to replace Bi at the A position in Bi3TiNbO9 3+ ions, with a hexa-coordinated Zn 2+ , Sb 5+ Sn 4+ 、Mo 6+ Composition of complex high-valent ions [Zn 0.25 Sb 0.75 ] 4.25+ 、[Sn 0.35 Mo 0.65 ] 5.3+ Doping Ti to replace the B position in Bi3TiNbO9 4+ , Nb 5+ ions, the chemical formula is Bi 3-x [Cd0.15 Sm 0.15 Ce 0.7 ] x Ti 1-y [Zn 0.25 Sb 0.75 ] y Nb 1-z [Sn 0.35 Mo 0.65 ] z O9, where 0.05≤x≤0.08, 0.02≤y≤0.05, 0.04≤z≤0.08.

[0007] In the above scheme, the piezoelectric ceramic material of the present invention has a 33 ≥20.4pC / N,T C ≥895℃; Resistivity (ρ) ≥2.0×10 at 500℃ 7 Ω·cm, dielectric loss (tanδ) ≤ 0.30%; d after annealing at 800℃ 33 ≥17.0pC / N.

[0008] Another object of the present invention is achieved by the following technical solutions:

[0009] The method for preparing the above-mentioned Cd / Sm / Ce / Zn / Sb / Sn / Mo doped Bi3TiNbO9 high temperature piezoelectric ceramic material provided by the present invention comprises the following steps:

[0010] (1) Preparation of pre-synthesized precursor powder

[0011] Bi2O3, TiO2, Nb2O5, CdO, Sm2O3, CeO2, ZnO, Sb2O3, SnO2 and MoO3 are used as raw materials corresponding to Bi, Ti, Nb, Cd, Sm, Ce, Zn, Sb, Sn and Mo in the general chemical formula; the amount of Bi2O3 in the raw materials is 1.0-1.5wt% more than the stoichiometric amount in the general chemical formula, and the amounts of the other raw materials are the stoichiometric amounts in the general chemical formula; after the ingredients are prepared in this way, a ball milling treatment is carried out with anhydrous ethanol as a ball milling medium; the obtained material is dried, sieved, pressed and formed, and then placed in a sealed crucible for calcination; the calcined material is then ground and sieved, and then a second ball milling treatment is carried out; the obtained material is dried, ground and sieved to obtain a pre-synthesized precursor powder;

[0012] (2) Preparation of high temperature piezoelectric ceramic materials

[0013] The pre-synthesized precursor powder is loaded into a graphite mold, placed in a spark plasma sintering furnace and sintered using a two-step sintering method to obtain a carbon-containing sintered product; then the carbon-containing sintered product is placed in an ordinary high-temperature furnace under an air atmosphere for decarburization calcination treatment to obtain a decarburized sintered product; finally, the decarburized sintered product is polarized to obtain a high-temperature piezoelectric ceramic material.

[0014] Furthermore, in the step (1) of the preparation method of the present invention, the pressure of the pressing molding is 4-6Mpa; the calcination treatment is to heat up to 800-820°C at 5°C / min in an oxidizing atmosphere and keep warm for 3-5h. In the step (2), the two-step sintering method is to heat up to the first platform temperature of 840-860°C at 100°C / min under the conditions of a spark plasma sintering furnace pressure of 55-60MPa and a DC pulse current of 600-650A, keep warm for 1-2min, then cool to the second platform temperature of 740-760°C after 2-3min, keep warm for 8-10min, cool to 600°C at 50°C / min, stop the DC pulse current, release the pressure, and cool to room temperature with the furnace; the decarburization calcination treatment is to heat up to 650-700°C at 5°C / min in an air atmosphere, keep warm for 2.5-3h, and cool to room temperature with the furnace.

[0015] Furthermore, the polarization treatment in step (2) of the preparation method of the present invention is to first polish the surface of the decarbonized sintered product; then perform electrode coating treatment, that is, silver electrodes are applied to the upper and lower surfaces of the decarbonized sintered product after polishing; then heat it to 740-760°C at 5°C / min for calcination, keep it warm for 20-30 minutes, and cool it to room temperature with the furnace; finally, polarize it in high-temperature silicone oil at 160-180°C with a DC voltage of 10-15kV / mm for 25-35 minutes.

[0016] The product is made using the above-mentioned method for preparing Cd / Sm / Ce / Zn / Sb / Sn / Mo doped Bi3TiNbO9 high-temperature piezoelectric ceramic material.

[0017] The present invention has the following beneficial effects:

[0018] (1) In the process of preparing Bi3TiNbO9 piezoelectric ceramic materials, bismuth vacancies are inevitably formed due to the volatilization of bismuth at high temperature, thereby generating oxygen vacancy defects. In view of this phenomenon, the present invention adopts three measures: ① When mixing the ingredients, the amount of Bi raw material is added 1.0-1.5wt% more than the stoichiometric amount in the chemical formula to compensate for the volatilization of bismuth; ② The valence state is higher than that of A-site Bi. 3+ Ions with high complex high valence [Cd 0.15 Sm 0.15 Ce 0.7 ] 3.55+Doping and substitution can improve the mixing entropy of the material; ③ Using a valence ratio of B to Ti 4+ , Nb 5+ Ionic high composite ions [Zn 0.25 Sb 0.75 ] 4.25+ 、[Sn 0.35 Mo 0.65 ] 5.3+ Doping and substitution can further increase the mixing entropy of the material. The above measures ② and ③ can also make the A and B positions both have defects, making the perovskite layer (A m-1 B m O 3m+1 ) 2- Generates electrons, thereby strengthening the bismuth oxide layer (Bi2O2) 2+ and perovskite-like layers (A m-1 B m O 3m+1 ) 2- The above three measures can achieve the following goals: ① reduce the oxygen vacancy concentration to increase the resistivity; ② reduce the carrier concentration inside the ceramic to further increase the resistivity; ③ regulate the growth behavior of the grains to generate polarized nanodomains locally and enhance the piezoelectric activity. In this way, the Bi3TiNbO9 high-temperature piezoelectric ceramic material with excellent performance was finally obtained.

[0019] (2) The present invention adopts advanced spark plasma sintering technology, and the sintering process adopts a two-step sintering method. The sintering technology requires a low sintering temperature and a short sintering time, so the energy consumption is low. Moreover, after sintering, the grains are small and uniform, and the material density is high, so that Bi3TiNbO9 high-temperature piezoelectric ceramic materials with excellent performance can be obtained.

[0020] (3) The Cd / Sm / Ce / Zn / Sb / Sn / Mo doped Bi3TiNbO9 piezoelectric ceramic material of the present invention has a Curie temperature above 895°C and a piezoelectric constant d 33 ≥20.4pC / N, d after annealing at 800℃ 33 ≥17.0pC / N; resistivity ≥2.0×10 at 500℃ 7 Ω·cm, dielectric loss ≤0.30%. The material has good high temperature stability, can fully meet the application requirements of piezoelectric ceramic transducer elements in high temperature environments, and has broad application prospects in high temperature electronic equipment.

[0021] (4) The preparation method of the present invention adopts advanced ceramic preparation technology, has low firing temperature, low preparation cost, simple and easy process operation, and easy control of influencing factors. It is suitable for large-scale industrial production and is conducive to promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings:

[0023] Figure 1 is the XRD crystal phase spectrum of the piezoelectric ceramic materials of the embodiments of the present invention and the comparative examples;

[0024] Figure 2 is the piezoelectric constant d of the piezoelectric ceramic materials of the embodiment of the present invention and the comparative example 33 Curves changing with temperature. DETAILED DESCRIPTION

[0025] Embodiment 1:

[0026] This embodiment is a Cd / Sm / Ce / Zn / Sb / Sn / Mo doped Bi3TiNbO9 high temperature piezoelectric ceramic material, the general chemical formula of which is Bi 2.95 [Cd 0.15 Sm 0.15 Ce 0.7 ] 0.05 Ti 0.98 [Zn 0.25 Sb 0.75 ] 0.02 Nb 0.96 [Sn 0.35 Mo 0.65 ] 0.04 O9, the preparation method of the piezoelectric ceramic material comprises the following steps:

[0027] (1) Preparation of pre-synthesized precursor powder

[0028] Bi2O3, TiO2, Nb2O5, CdO, Sm2O3, CeO2, ZnO, Sb2O3, SnO2 and MoO3 with a purity of 99.9% are used as raw materials corresponding to Bi, Ti, Nb, Cd, Sm, Ce, Zn, Sb, Sn and Mo in the above chemical formula; the amount of Bi2O3 in the above raw materials is 1.0wt% more than the stoichiometric amount in the chemical formula, and the amounts of the other raw materials are the stoichiometric amounts in the chemical formula. After the ingredients are prepared in this way, anhydrous ethanol is used as the ball milling medium, and the ratio of ball: material: anhydrous ethanol is used. alcohol = 4:1:3, a ball milling treatment is carried out on a planetary ball mill at a speed of 400r / min for 24h, the obtained material is dried, passed through an 80-mesh sieve, pressed and formed under a pressure of 4Mpa, and placed in a sealed crucible, and the temperature is increased to 800℃ at 5℃ / min in an oxidizing atmosphere for calcination, and the heat preservation time is 3h; then the calcined material is ground and passed through an 80-mesh sieve, and a secondary ball milling treatment is carried out using the same process as the primary ball milling treatment, and the obtained material is dried, ground, and passed through an 80-mesh sieve to obtain a pre-synthesized precursor powder;

[0029] (2) Preparation of high temperature piezoelectric ceramic materials

[0030] (2-1) 0.8 g of the above-mentioned pre-synthesized precursor powder was loaded into a cylindrical graphite mold with a diameter of 20 mm, and placed in a spark plasma sintering furnace. Under the conditions of a pressure of 55 MPa and a DC pulse current of 600 A, the temperature was first raised to a first platform temperature of 840° C. at a rate of 100° C. / min, and kept at that temperature for 1 min. Then, the temperature was rapidly cooled to a second platform temperature of 740° C. over 2 min, and kept at that temperature for 8 min. Then, the temperature was reduced to 600° C. at a rate of 50° C. / min, the DC pulse current was stopped, and then the pressure was released. The product was cooled to room temperature along with the furnace to obtain a carbon-containing sintered product.

[0031] (2-2) placing the carbon-containing sintered product in a common high-temperature furnace, heating the product to 650° C. at a rate of 5° C. / min in an air atmosphere for decarburization calcination, keeping the temperature for 3 h, and cooling the product to room temperature to obtain a decarburized sintered product;

[0032] (2-3) The decarburized sintered product is subjected to the following polarization treatment: first, the surface of the decarburized sintered product is polished; then, electrode coating is performed, i.e., silver electrodes are applied to the upper and lower surfaces of the decarburized sintered product after polishing; then, the temperature is raised to 750°C at a rate of 5°C / min for calcination, the temperature is kept at this temperature for 20 minutes, and the product is cooled to room temperature with the furnace; finally, the product is polarized in high-temperature silicone oil at 160°C with a DC voltage of 10 to 15 kV / mm for 25 minutes, thereby obtaining a high-temperature piezoelectric ceramic material.

[0033] Embodiment 2:

[0034] This embodiment is a Cd / Sm / Ce / Zn / Sb / Sn / Mo doped Bi3TiNbO9 high temperature piezoelectric ceramic material and a preparation method thereof, which is different from the first embodiment in that:

[0035] (1) The general chemical formula of the piezoelectric ceramic material of this embodiment is Bi 2.92 [Cd 0.15 Sm 0.15 Ce 0.7 ] 0.08 Ti 0.97 [Zn 0.25 Sb 0.75 ] 0.03 Nb 0.96 [Sn 0.35 Mo 0.65 ] 0.04 O9.

[0036] (2) The calcination temperature in step (1) of the preparation method of this embodiment is 820°C.

[0037] (3) The calcination system in step (2-1) of the preparation method of this embodiment is: under the conditions of a pressure of 60 MPa and a DC pulse current of 650 A, the temperature is first raised to a first platform temperature of 850° C. at a rate of 100° C. / min, kept at that temperature for 1 min, then rapidly cooled to a second platform temperature of 750° C. over 2 min, kept at that temperature for 10 min, then cooled to 600° C. at a rate of 50° C. / min, the DC pulse current is stopped, and then the pressure is released and the product is cooled to room temperature in the furnace to obtain a carbon-containing sintered product.

[0038] Embodiment three:

[0039] This embodiment is a Cd / Sm / Ce / Zn / Sb / Sn / Mo doped Bi3TiNbO9 high temperature piezoelectric ceramic material and a preparation method thereof, which is different from the first embodiment in that:

[0040] (1) The general chemical formula of the piezoelectric ceramic material of this embodiment is Bi 2.94 [Cd 0.15 Sm 0.15 Ce 0.7 ] 0.06 Ti 0.96 [Zn 0.25 Sb 0.75 ] 0.04 Nb 0.94 [Sn 0.35 Mo 0.65 ] 0.06 O9.

[0041] (2) The calcination temperature in step (1) of the preparation method of this embodiment is 820°C.

[0042] (3) The calcination system in step (2-1) of the preparation method of this embodiment is: under the conditions of a pressure of 60 MPa and a DC pulse current of 650 A, the temperature is first raised to a first platform temperature of 860° C. at a rate of 100° C. / min, kept at that temperature for 1.5 min, then rapidly cooled to a second platform temperature of 760° C. over 2 min, kept at that temperature for 8 min, then cooled to 600° C. at a rate of 50° C. / min, the DC pulse current is stopped, and then the pressure is released and the product is cooled to room temperature in the furnace to obtain a carbon-containing sintered product.

[0043] Comparative Example:

[0044] An undoped high temperature piezoelectric ceramic material having the general chemical formula Bi3TiNbO9 is used as a comparative example, and its preparation method is the same as that of the first embodiment.

[0045] The XRD crystal phase spectra of the piezoelectric ceramic materials of the embodiments of the present invention and the comparative examples are as follows: Figure 1 As shown, from Figure 1It can be seen that the diffraction peaks of the piezoelectric ceramic materials prepared in the embodiments and comparative examples are completely consistent with the standard spectrum PDF 00-039-0233, indicating that the obtained materials are Bi3TiNbO9 materials with a single crystal phase.

[0046] Piezoelectric constant d of piezoelectric ceramic materials in the embodiments of the present invention and the comparative examples 33 The temperature change curve is as follows Figure 2 As shown. Figure 2 It can be seen that from room temperature to 600°C, the d 33 The value decreases slightly with the increase of temperature. At 800℃, d 33 The value still remains above 83.3% of that at room temperature, indicating that the material has good temperature stability and is conducive to its application in high temperature fields.

[0047] The performance test results of the piezoelectric ceramic materials of the embodiments of the present invention and the comparative examples are shown in Table 1.

[0048] Table 1 Performance indicators of ceramic materials of the embodiments of the present invention and comparative examples

[0049]

Claims

1. A Cd / Sm / Ce / Zn / Sb / Sn / Mo doped Bi3TiNbO9 high temperature piezoelectric ceramic material, characterized in that: With 12-coordinated Cd 2+ 、Sm 3+ 、Ce 4+ The complex high-valent ions [Cd 0.15 Sm 0.15 Ce 0.7 ] 3.55+ Doping to replace Bi at the A position in Bi3TiNbO9 3+ ions, with a hexa-coordinated Zn 2+ , Sb 5+ Sn 4+ 、Mo 6+ Composition of complex high-valent ions [Zn 0.25 Sb 0.75 ] 4.25+ 、[Sn 0.35 Mo 0.65 ] 5.3+ Doping Ti to replace the B position in Bi3TiNbO9 4+ , Nb 5+ ions, the chemical formula is Bi 3-x [Cd 0.15 Sm 0.15 Ce 0.7 ] x Ti 1-y [Zn 0.25 Sb 0.75 ] y Nb 1-z [Sn 0.35 Mo 0.65 ] z O9, where 0.05≤x≤0.08, 0.02≤y≤0.05, 0.04≤z≤0.

08.

2. The Cd / Sm / Ce / Zn / Sb / Sn / Mo doped Bi3TiNbO9 high temperature piezoelectric ceramic material according to claim 1, characterized in that: The d of the piezoelectric ceramic material 33 ≥20.4pC / N,T C ≥895℃; Resistivity (ρ) ≥2.0×10 at 500℃ 7 Ω·cm, dielectric loss (tanδ) ≤ 0.30%; d after annealing at 800℃ 33 ≥17.0pC / N.

3. The method for preparing the Cd / Sm / Ce / Zn / Sb / Sn / Mo doped Bi3TiNbO9 high temperature piezoelectric ceramic material according to claim 1 or 2, characterized in that The following steps are involved: (1) Preparation of pre-synthesized precursor powder Bi2O3, TiO2, Nb2O5, CdO, Sm2O3, CeO2, ZnO, Sb2O3, SnO2 and MoO3 are used as raw materials corresponding to Bi, Ti, Nb, Cd, Sm, Ce, Zn, Sb, Sn and Mo in the general chemical formula; the amount of Bi2O3 in the raw materials is 1.0-1.5wt% more than the stoichiometric amount in the general chemical formula, and the amounts of the other raw materials are the stoichiometric amounts in the general chemical formula; after the ingredients are prepared in this way, they are subjected to a ball milling treatment using anhydrous ethanol as a ball milling medium; the obtained materials are dried, sieved and pressed into shape, and then placed in a sealed crucible for calcination treatment; the calcined materials are then ground and sieved, and then subjected to a secondary ball milling treatment; the obtained materials are dried, ground and sieved to obtain a pre-synthesized precursor powder; (2) Preparation of high temperature piezoelectric ceramic materials The pre-synthesized precursor powder is loaded into a graphite mold, placed in a spark plasma sintering furnace and sintered using a two-step sintering method to obtain a carbon-containing sintered product; then the carbon-containing sintered product is placed in an ordinary high-temperature furnace under an air atmosphere for decarburization calcination treatment to obtain a decarburized sintered product; finally, the decarburized sintered product is polarized to obtain a high-temperature piezoelectric ceramic material.

4. The method for preparing the Cd / Sm / Ce / Zn / Sb / Sn / Mo doped Bi3TiNbO9 high temperature piezoelectric ceramic material according to claim 3, characterized in that: The pressure of the pressing molding in the step (1) is 4-6 MPa; the calcination treatment is carried out by heating the temperature to 800-820° C. at 5° C. / min in an oxidizing atmosphere and keeping the temperature for 3-5 hours.

5. The method for preparing the Cd / Sm / Ce / Zn / Sb / Sn / Mo doped Bi3TiNbO9 high temperature piezoelectric ceramic material according to claim 3, characterized in that: The two-step sintering method in step (2) is as follows: under the conditions of a spark plasma sintering furnace pressure of 55-60 MPa and a DC pulse current of 600-650 A, the temperature is first raised to a first platform temperature of 840-860° C. at a rate of 100° C. / min, kept at that temperature for 1-2 min, then cooled to a second platform temperature of 740-760° C. after 2-3 min, kept at that temperature for 8-10 min, then cooled to 600° C. at a rate of 50° C. / min, the DC pulse current is stopped, and then the pressure is released and the furnace is cooled to room temperature; the decarburization calcination treatment is carried out by raising the temperature to 650-700° C. at a rate of 5° C. / min in an air atmosphere, keeping at that temperature for 2.5-3 h, and then cooling to room temperature with the furnace.

6. The method for preparing the Cd / Sm / Ce / Zn / Sb / Sn / Mo doped Bi3TiNbO9 high temperature piezoelectric ceramic material according to claim 3, characterized in that: The polarization treatment in step (2) is as follows: first, the surface of the decarburized sintered product is polished; then, an electrode coating treatment is performed, i.e., silver electrodes are applied to the upper and lower surfaces of the decarburized sintered product after polishing; then, the temperature is raised to 740-760°C at 5°C / min for calcination, the temperature is kept at this temperature for 20-30 minutes, and the product is cooled to room temperature with the furnace; finally, the product is polarized in high-temperature silicone oil at 160-180°C with a DC voltage of 10-15 kV / mm for a polarization time of 25-35 minutes.

7. A product obtained by the method for preparing Cd / Sm / Ce / Zn / Sb / Sn / Mo doped Bi3TiNbO9 high temperature piezoelectric ceramic material as claimed in any one of claims 3 to 6.

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