A bismuth-based composite high-temperature resistant piezoelectric ceramic material and its preparation method

Abstract

The present invention discloses a bismuth-based composite high-temperature resistant piezoelectric ceramic material and a preparation method thereof. The bismuth-based composite high-temperature resistant piezoelectric ceramic material is composed of Ca2+ with an ultra-high Curie temperature. 1‑x‑y (A1 x A2 y )Bi2(Nb) 2‑m‑n (B1 m B2 n )O9 bismuth layered piezoelectric ceramics and (Na 0.5‑p‑q A3 p A4 q )Bi i Nb2O9-based bismuth layered piezoelectric ceramics or bismuth-based perovskite structure high-temperature piezoelectric ceramics Bi a Pb 1‑ a Zn 0.5a Ti 1‑0.5a O3 composite. Through a series of processes including powder pre-synthesis, proportional mixing, ball milling, molding, and oxygen sintering, a highly dense composite ceramic material is obtained. Furthermore, by subjecting the resulting ceramic material to secondary polarization, secondary aging, and thermal cycling treatment, a high-temperature-resistant piezoelectric composite ceramic material with high piezoelectric properties, high resistivity, low dielectric loss, and high temperature stability is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of piezoelectric ceramic materials, and in particular relates to a bismuth-based composite high-temperature resistant piezoelectric ceramic material and a preparation method thereof. Background Art

[0002] Piezoelectric ceramics are functional materials that can realize the mutual conversion of mechanical energy and electrical energy. PZT piezoelectric ceramics are the most typical piezoelectric materials. They have the characteristics of high piezoelectric coefficient and excellent mechanical quality factor, and have been widely used in ultrasonic devices, sensors, transducers and other fields. With the continuous development of science and technology, many fields such as energy, aerospace, and defense industry have put forward huge application demands for piezoelectric materials that can work in high-temperature environments. However, traditional PZT piezoelectric ceramics are prone to depolarization above 200°C and cannot meet the needs of practical applications. Therefore, it is of great value to study high-temperature piezoelectric ceramics that can be used in high-temperature environments.

[0003] Typical piezoelectric ceramic material systems include perovskite, tungsten bronze, bismuth layered, etc. In comparison, bismuth layered piezoelectric ceramics have advantages such as high Curie temperature (usually >500°C), strong spontaneous polarization, low dielectric loss, high resistivity, and low aging rate, and have great application prospects in fields such as high-temperature vibration sensors. Common bismuth layered high-temperature piezoelectric systems include Bi4Ti3O 12 (Curie temperature is about 637 ℃, d 33 About 16 pC / N), Na 0.5 Bi 2.5 Nb2O9 (Curie temperature is about 776 ℃, d 33 About 10 pC / N), CaBi2Nb2O9 (Curie temperature is about 936 ℃, d 33 However, bismuth layered piezoelectric ceramics generally have disadvantages such as low piezoelectric activity and high coercive electric field, making it difficult to simultaneously meet the requirements of operating in a suitable high-temperature (500°C) environment and maintaining stable comprehensive electrical properties.

[0004] In order to improve the electrical properties of bismuth layered piezoelectric ceramics, most current studies use ion doping or microstructure control to optimize performance. Ion doping can be used to appropriately reduce the oxygen vacancy concentration of the material, thereby increasing the resistivity or the spontaneous polarization strength of the material. Microstructure control is mainly achieved by controlling the grain size or using a texturing process to arrange the ceramic grains in a certain orientation, thereby enhancing the piezoelectric performance in a specific direction. Although the above methods can improve the performance of piezoelectric ceramics, the process requirements are high, and the high-voltage electrical activity and high resistivity of the ceramic material are not stable enough at high temperatures. Therefore, how to obtain bismuth layered piezoelectric ceramic materials with high temperature stability, high-voltage electrical activity, and high resistivity is of great value. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the comprehensive electrical properties of piezoelectric ceramic materials in the prior art, such as the unstable high-temperature performance of the materials and the inability to work stably for a long time in a high-temperature environment, and to provide a bismuth-based composite high-temperature resistant piezoelectric ceramic material with high high-voltage electrical activity, high resistivity and high temperature stability and a preparation method thereof.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A bismuth-based composite high-temperature resistant piezoelectric ceramic material, composed of bismuth layered piezoelectric ceramic Ca 1-x-y (A1 x A2 y )Bi2(Nb) 2-m-n (B1 m B2 n )O9 and bismuth-based high-temperature piezoelectric ceramic material M composite composition;

[0008] A1 is Li, A2 is Nd or Sm, B1 is Mn, and B2 is W; wherein: x is 0.04 or 0.05; y is 0.04 or 0.05; m is 0.0025 or 0; and n is 0.0075 or 0.02.

[0009] Furthermore, the bismuth-based high-temperature piezoelectric ceramic material M is a bismuth layered piezoelectric ceramic (Na 0.5-p-q A3 p A4 q )Bi i Nb2O9 or Bi a Pb 1-a Zn 0.5a Ti 1-0.5a O3; A3 is alkali metal Li, A4 is Ce; p is 0.05; q is 0.05; i is 2.38; and a is 0.35.

[0010] Furthermore, the chemical formula of the bismuth-based composite high-temperature resistant piezoelectric ceramic material is:

[0011] z1[Ca 1-x-y (A1 x A2 y )Bi2(Nb) 2-m-n (B1 m B2 n )O9]-(1-z1)[(Na 0.5-p-q A3 p A4 q )Bi i Nb2O9] or

[0012] z2[Ca1-x-y (A1 x A2 y )Bi2(Nb) 2-m-n (B1 m B2 n )O9]-(1-z2)[Bi a Pb 1-a Zn 0.5a Ti 1-0.5a O3], wherein z1 is 0.1 or 0.2; z2 is 0.9.

[0013] Furthermore, the bismuth-based composite high-temperature resistant piezoelectric ceramic material has a piezoelectric coefficient of (15-30) pC / N at room temperature, a room-temperature dielectric constant of 100-160 at 1 kHz, a room-temperature dielectric loss of 0.002-0.01 at 1 kHz, and a resistivity of (10 5 ~10 8 ) Ωcm; the change rate of the dielectric constant, dielectric loss and piezoelectric coefficient of the bismuth-based composite high-temperature resistant piezoelectric ceramic material after 500 ℃ insulation treatment is less than 1%.

[0014] The method for preparing the above-mentioned bismuth-based composite high-temperature resistant piezoelectric ceramic material comprises the following steps:

[0015] Step 1: Prefabricate Ca 1-x-y (A1 x A2 y )Bi2(Nb) 2-m-n (B1 m B2 n ) O9 ceramic powder: using various metal oxides, carbonates or nitrates as raw materials according to the chemical formula ratio, weighing, mixing, ball milling, drying, briquetting, calcining and crushing to obtain a pre-synthesized powder;

[0016] Step 2, Prefabrication (Na 0.5-p-q A3 p A4 q )Bi i Nb2O9 ceramic powder or Bi a Pb 1-a Zn 0.5a Ti 1-0.5a O3 ceramic powder: using various metal oxides, carbonates or nitrates as raw materials according to the chemical formula ratio, weighing, mixing, ball milling, drying, briquetting, calcining and crushing to obtain pre-synthesized ceramic powder;

[0017] Step 3: The ceramic powders pre-synthesized in Steps 1 and 2 are weighed in a molar ratio of z:(1-z), ball-milled, and dried to obtain a powder having a median particle size D50 of 1 to 2 μm. A binder is added to the powder, and the powder is granulated and pressed to obtain a ceramic green sheet;

[0018] Step 4: Debinding the ceramic green sheet obtained in step 3 to obtain an intermediate product;

[0019] Step 5: Spread the intermediate product on a pad and place it in an atmosphere furnace to introduce oxygen for sintering. The oxygen flow rate is 0.6-1.0 L / min, the sintering heating rate is 2-10 °C / min, the sintering temperature is 1050-1200 °C, and the holding time is 1-4 hours. After sintering, cool it in the furnace to obtain a ceramic material.

[0020] Step 6: Polish the ceramic material on both sides, clean it and dry the printed electrodes;

[0021] Step 7: subjecting the prepared electrode ceramic material to a first polarization treatment;

[0022] Step 8, performing a first aging treatment on the ceramic material after the first polarization;

[0023] Step 9: subjecting the ceramic material after the first aging treatment to a second polarization treatment at the same polarity as the first polarization treatment, wherein the second polarization temperature is 160-220° C., the polarization electric field is 120-220 kV / cm, and the polarization time is 20-60 minutes;

[0024] Step 10: The ceramic material after the secondary polarization is subjected to a second aging treatment. The second aging treatment is as follows: the ceramic material after the second polarization is heated from room temperature to 550-600°C, kept warm for 24-48 hours, and then subjected to 2-5 heating and cooling thermal cycles from the current temperature to -60°C, with a heating and cooling rate of 2-5°C / minute, to obtain a bismuth-based composite high-temperature resistant piezoelectric ceramic material.

[0025] Furthermore, in step 5, the oxygen flow rate is 0.8 L / min, the sintering heating rate is 5° C. / min, and the sintering temperature is 1120° C.

[0026] Furthermore, in step 6, when printing the electrode, the firing temperature of the electrode is 700-1000° C., and the holding time is 10-60 minutes.

[0027] Furthermore, in step 7, the polarization temperature during the first polarization treatment is 160-220° C., the polarization electric field is 120-220 kV / cm, and the polarization time is 20-60 minutes.

[0028] Furthermore, in step 8, the ceramic material after the first polarization is heated to 500-600° C., kept at this temperature for 24-48 hours, and then cooled to room temperature to complete the first aging treatment.

[0029] Furthermore, in step 10, the second aging treatment is: raising the temperature of the ceramic material after the second polarization from room temperature to 600°C, keeping it warm for 24 hours, and then performing two heating and cooling thermal cycles from 600°C to -60°C, with a heating and cooling rate of 5°C / minute, to obtain a bismuth-based composite high-temperature resistant piezoelectric ceramic material.

[0030] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0031] The present invention combines CaBi2Nb2O9-based bismuth layered piezoelectric ceramics with high resistivity and low piezoelectric performance with modified Na 0.5 Bi 2.5 Nb2O9-based bismuth layered structure or Bi a Pb 1-a Zn 0.5a Ti 1-0.5a The composite ceramic combines the high-voltage and high-resistivity advantages of different materials while mitigating the respective shortcomings of the two raw materials. This allows for complementary and optimized resistivity and piezoelectric performance, and promotes sintering to achieve a highly dense ceramic material. The composite ceramic effectively enhances the piezoelectric performance of the ceramic material while maintaining a high Curie temperature and resistivity.

[0032] The preparation method of the bismuth-based composite high-temperature resistant piezoelectric ceramic material provided by the present invention adopts the method of passing oxygen during sintering. The oxygen passing at a certain flow rate effectively reduces the oxygen vacancies generated during the high-temperature sintering process of the ceramic material, thereby obtaining a ceramic material with high resistivity and high piezoelectricity at high temperature.

[0033] Furthermore, the present invention, based on conventional piezoelectric ceramic primary polarization, performs high-temperature secondary polarization, secondary aging, and thermal cycling. This not only fully polarizes the ceramic material to produce a composite ceramic material with high piezoelectric properties, but also significantly improves the high-temperature stability of the composite ceramic material's dielectric and piezoelectric properties. The developed ceramic material has promising application prospects in the field of high-temperature piezoelectrics.

[0034] The preparation method of the present invention is easy to operate, simpler than the high-temperature piezoelectric single crystal process, and suitable for promotion and large-scale use.

[0035] Testing has shown that the high-temperature piezoelectric composite ceramic material obtained using this invention exhibits good ceramic density, a high piezoelectric coefficient, high high-temperature resistivity, a high dielectric constant, low dielectric loss, and a high Curie temperature. This composite ceramic material can be used to manufacture ceramic components of various shapes and assembled into various piezoelectric sensors and transducers, finding widespread application in measurement, detection, and control at temperatures of 500°C and even higher. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A flow chart of a method for preparing a bismuth-based composite high-temperature resistant piezoelectric ceramic material provided by the present invention;

[0037] Figure 2 XRD patterns of the high-temperature piezoelectric ceramics prepared in Examples 1 to 3;

[0038] Figure 3 The SEM images of the high-temperature piezoelectric ceramics prepared in Examples 1 to 3 are shown;

[0039] Figure 4 The graph shows the relationship between the resistivity and temperature of the high-temperature piezoelectric ceramics prepared in Examples 1 to 3. DETAILED DESCRIPTION

[0040] In order to make the purpose and technical solution of the present invention clearer and easier to understand, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0041] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more. In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0042] A bismuth-based composite high-temperature resistant piezoelectric ceramic material is composed of a CaBi2Nb2O9-based bismuth layered structure piezoelectric ceramic and a bismuth-based high-temperature piezoelectric ceramic material M.

[0043] The chemical formula of the CaBi2Nb2O9 based piezoelectric ceramic is Ca 1-x-y (A1 x A2 y )Bi2(Nb) 2-m-n (B1 m B2 n )O9, wherein A1 is at least one of the alkali metals Li, Na, and K, A2 is at least one of the rare earth elements Nd, Sm, Ce, Pr, La, Er, and Tb, B1 is at least one of the variable-valence metals Mn, Ni, Co, and Cu, and B2 is at least one of W and Mo. Wherein x is 0.04 or 0.05; y is 0.04 or 0.05; m is 0.0025 or 0; and n is 0.0075 or 0.02.

[0044] One of the choices of Bi-based high temperature piezoelectric ceramic material M is modified Na 0.5 Bi 2.5 Nb2O9 based bismuth layered piezoelectric ceramics (Na 0.5-p-q A3 p A4 q )Bi i Nb2O9. A3 is at least one of the alkali metals Li, Na, and K, and A4 is at least one of the rare earth elements Nd, Sm, Ce, Pr, La, Er, and Tb. In the formula, p is 0.05; q is 0.05; and i is 2.38.

[0045] The second choice of bismuth-based high-temperature piezoelectric ceramic material M is bismuth-based perovskite structure high-temperature piezoelectric ceramic Bi a Pb 1- a Zn 0.5a Ti 1-0.5a O3, where a is 0.35.

[0046] The third choice of bismuth-based high-temperature piezoelectric ceramic material M is bismuth-based perovskite structure high-temperature piezoelectric ceramic Bi b Pb 1- b Fe b Ti 1-b O3, where 0.6 <b≤1 。

[0047] Furthermore, the chemical formula of the composite high temperature piezoelectric ceramic material is: z1[Ca 1-x-y (A1 x A2 y )Bi2(Nb) 2-m-n (B1 m B2 n )O9]-(1-z1)[(Na 0.5-p-q A3 p A4 q)Bi i Nb2O9] or z2[Ca 1-x-y (A1 x A2 y )Bi2(Nb) 2-m-n (B1 m B2 n )O9]-(1-z2)[Bi a Pb 1-a Zn 0.5a Ti 1-0.5a O3], where z1 is 0.1 or 0.2, and z2 is 0.9.

[0048] A high-temperature resistant piezoelectric composite ceramic material is prepared by the following method:

[0049] Step 1: Prefabricate Ca 1-x-y (A1 x A2 y )Bi2(Nb) 2-m-n (B1 m B2 n )O9 ceramic powder. Using metal oxides, carbonates, or nitrates with a purity greater than 99% as raw materials, according to the proportions shown in the chemical formula, the raw materials are weighed, mixed, ball-milled, dried, pressed into blocks, calcined, and crushed to obtain a pre-synthesized powder. The ball-milling medium used is anhydrous ethanol or deionized water. Calcination conditions are 700-1000°C for 2-6 hours.

[0050] Step 2, Prefabrication (Na 0.5-p-q A3 p A4 q )Bi i Nb2O9 ceramic powder, Bi a Pb 1-a Zn 0.5a Ti 1-0.5a O3 ceramic powder or Bi b Pb 1-b Fe b Ti 1-b O3 ceramic powder. Using metal oxides, carbonates, or nitrates with a purity greater than 99% as raw materials, according to the chemical formula, the pre-synthesized ceramic powder is weighed, mixed, ball-milled, dried, pressed into blocks, calcined, and crushed. The ball-milling medium used is anhydrous ethanol. Calcination conditions are 600-1000°C for 2-6 hours.

[0051] Step 3: The ceramic powders pre-synthesized in Steps 1 and 2 are weighed at a molar ratio of z:(1-z) and ball-milled, where z ranges from 0.1 to 0.2. The milling medium used is anhydrous ethanol, and the milling time is 15 to 48 hours. After ball milling, the slurry is dried to obtain a powder with a median particle size D50 of 1 to 2 microns. A 4% to 10% polyvinyl alcohol solution is added to the dried powder as a binder, and the mixture is granulated and pressed to obtain ceramic green sheets.

[0052] Step 4: Place the ceramic green sheet obtained in step 3 into an electric furnace for debinding treatment. The heating rate used for debinding is 2-8°C / min, the temperature is 400-700°C, and the holding time is 0.5-2 hours.

[0053] Step 5: Spread the debinded sample flat on an alumina or zirconia backing plate and place it in an atmosphere furnace, introducing oxygen for sintering. The oxygen flow rate is 0.6-1.0 L / min, the sintering heating rate is 2-10°C / min, the sintering temperature is 1050-1200°C, and the holding time is 1-4 hours. After sintering, cool the sample in the furnace to obtain a ceramic material.

[0054] Step 6: Polish both sides of the oxygen-sintered ceramic material, clean it, dry it, and then print the platinum electrodes. The platinum electrodes are fired at a temperature of 700-1000°C for 10-60 minutes.

[0055] Step 7: The ceramic material of the prepared electrode is subjected to the first polarization treatment in high-temperature silicone oil at a polarization temperature of 160-220°C, a polarization electric field of 120-220 kV / cm, and a polarization time of 20-60 minutes.

[0056] Step 8: Raise the temperature of the ceramic material after the first polarization to 500-600°C, keep it at this temperature for 24-48 hours, and then cool it down to room temperature to complete the first aging treatment.

[0057] Step 9: The aged ceramic material is subjected to a second polarization treatment using the same polarity as the first polarization, with a polarization temperature of 160-220°C, a polarization electric field of 120-220 kV / cm, and a polarization time of 20-60 minutes. The purpose of the second polarization treatment is to further improve the piezoelectric properties of the resulting piezoelectric ceramic material.

[0058] Step 10: The second polarized ceramic material undergoes a second aging process. This second aging process involves first heating the temperature from room temperature to 550-600°C, holding for 24-48 hours, and then performing two thermal cycles from this temperature to -60°C at a rate of 2-5°C / minute. This second aging process aims to improve the high-temperature stability of the piezoelectric ceramic's electrical properties and reduce stress in the ceramic.

[0059] Piezoelectric coefficient d of composite high-temperature piezoelectric ceramic materials at room temperature 33 The room temperature dielectric constant ε at 1 kHz is (15~30) pC / N. r The room temperature dielectric loss tanδ at 1 kHz is 0.002~0.01, and the resistivity at 450~500 ℃ is (10 5 ~10 8 )Ωcm. The dielectric constant ε after heat treatment at 500℃ for 30-60 minutes r , dielectric loss tanδ and piezoelectric coefficient d 33 The rate of change is less than 1%.

[0060] Example 1

[0061] The bismuth-based composite high-temperature resistant piezoelectric ceramic material provided in this embodiment is: 0.2[(Ca 0.92 Li 0.04 Nd 0.04 )Bi2Nb 1.99 Mn 0.0025 W 0.0075 O9]-0.8[(Na 0.4 Li 0.05 Ce 0.05 )Bi 2.38 Nb2O9] composite ceramics, wherein the subscript numbers represent the molar ratios of the elements.

[0062] Reference Figure 1 The preparation method of bismuth-based composite high-temperature resistant piezoelectric ceramic material comprises the following steps:

[0063] Step 1: 99% pure CaCO3, 99.9% Li2CO3, 99.99% Nd2O3, 99.9% Bi2O3, 99.99% Nb2O5, 99.9% MnO, 99.9% WO3 are mixed in a sieve according to the following formula: 0.92 Li 0.04 Nd 0.04 )Bi2Nb 1.99 Mn 0.0025 W 0.0075 The mixture was weighed in the proportion shown in FIG09, and a certain proportion of zirconium balls was added. The mixture was milled for 20 hours using a planetary ball mill. The medium used for the milling was anhydrous ethanol. The mixture was dried, pressed into a block, placed in an alumina crucible with a lid, and calcined in a muffle furnace at 850°C for 4 hours. After cooling, the mixture was taken out and crushed to obtain Ca 1-x-y (A1 x A2 y )Bi2(Nb) 2-m-n (B1 mB2 n )O9 ceramic powder.

[0064] Step 2: 99.9% purity Na2CO3, 99.9% Li2CO3, 99.99% CeO2, 99.9% Bi2O3, 99.99% Nb2O5 are mixed in the following manner: 0.4 Li 0.05 Ce 0.05 )Bi 2.38 The mixture was weighed in the proportion shown in FIG. 1 , and a certain proportion of zirconium balls was added. The mixture was milled for 20 hours using a planetary ball mill. The medium used for the milling was anhydrous ethanol. The mixture was dried, pressed into a block, placed in an alumina crucible with a lid, and calcined in a muffle furnace at 850° C. for 3 hours. After cooling, the mixture was taken out and crushed to obtain (Na 0.5-p-q A3 p A4 q )Bi i Nb2O9 ceramic powder.

[0065] Step 3: The ceramic powders pre-synthesized in Steps 1 and 2 were weighed at a molar ratio of 0.2:0.8 and placed in a ball mill. Zirconia balls and anhydrous ethanol were added in a certain proportion and ball milled for 20 hours. After ball milling, the slurry was dried at 60°C for 24 hours, resulting in a powder with a median particle size (D50) of less than 2 microns. A 5% polyvinyl alcohol solution was added to the dried powder as a binder, and the powder was granulated and pressed to produce ceramic green sheets with a diameter of 12 mm.

[0066] Step 4: Place the ceramic green sheet obtained in step 3 into an electric furnace for debinding treatment. The heating rate used for debinding is 5°C / min, the temperature is 600°C, and the holding time is 1 hour.

[0067] Step 5: Spread the debinded sample flat on an alumina or zirconia pad and place it in an atmosphere furnace to sinter with oxygen. The oxygen flow rate is 0.8 L / min, the sintering heating rate is 5 ℃ / min, the sintering temperature is 1120 ℃, and the holding time is 3 hours. After sintering, the ceramic material is cooled in the furnace. The powder X-ray diffraction results of the obtained composite ceramic material are shown in Figure 2. Figure 2 The surface morphology of the obtained ceramic material is shown in Figure 3 shown.

[0068] Step 6: The oxygen-sintered ceramic material is double-sided polished and then ultrasonically cleaned. After cleaning, it is dried at 120°C and then printed with platinum slurry. The platinum electrodes are fired at 800°C for 30 minutes to ensure good ohmic contact between the ceramic and the electrodes.

[0069] Step 7: The prepared electrode ceramic material is subjected to the first polarization treatment in high-temperature silicone oil at a polarization temperature of 200°C, a polarization electric field of 150 kV / cm, and a polarization time of 30 minutes.

[0070] Step 8: Raise the temperature of the ceramic material after the first polarization to 500°C and keep it at this temperature for 24 hours to complete the first aging treatment.

[0071] Step 9: The ceramic material after the first aging is subjected to a second polarization treatment with the same polarity as the first polarization, the polarization temperature is 200°C, the polarization electric field is 200 kV / cm, and the polarization time is 30 minutes.

[0072] Step 10: The ceramic material after secondary polarization is subjected to a second aging process. The aging process is to first increase the temperature from room temperature to 600°C, keep the temperature for 24 hours, and then perform two heating and cooling cycles from 600°C to -60°C at a heating and cooling rate of 5°C / minute.

[0073] The aged ceramic material was subjected to quasi-static 33 Tester, impedance analyzer to test its piezoelectric coefficient d 33 , Planar electromechanical coupling coefficient k p , dielectric constant ε r , dielectric loss tanδ, the results are shown in Table 1. The resistivity of ceramic materials at different temperatures was tested using a Keithley 6517B high resistance meter. The results are shown in Table 1. Figure 4 shown.

[0074] Example 2

[0075] The bismuth-based composite high-temperature resistant piezoelectric ceramic material provided in this embodiment is:

[0076] 0.9[(Ca 0.92 Li 0.04 Nd 0.04 )Bi2Nb 1.99 Mn 0.0025 W 0.0075 O9]-0.1[(Na 0.4 Li 0.05 Ce 0.05 )Bi 2.38 Nb2O9] composite ceramics, wherein the subscript numbers represent the molar ratio of the elements.

[0077] A method for preparing a bismuth-based composite high-temperature resistant piezoelectric ceramic material comprises the following steps:

[0078] Step 1: 99% pure CaCO3, 99.9% Li2CO3, 99.99% Nd2O3, 99.9% Bi2O3, 99.99% Nb2O5, 99.9% MnO, 99.9% WO3 are mixed in a sieve according to the following formula: 0.92 Li 0.04 Nd 0.04 )Bi2Nb 1.99 Mn 0.0025 W 0.0075 The mixture was weighed in the proportion shown in FIG09, and a certain proportion of zirconium balls was added. The mixture was milled for 20 hours using a planetary ball mill. The medium used for the milling was anhydrous ethanol. The mixture was dried, pressed into a block, placed in an alumina crucible with a lid, and calcined in a muffle furnace at 850°C for 4 hours. After cooling, the mixture was taken out and crushed to obtain Ca 1-x-y (A1 x A2 y )Bi2(Nb) 2-m-n (B1 m B2 n )O9 ceramic powder.

[0079] Step 2: 99.9% purity Na2CO3, 99.9% Li2CO3, 99.99% CeO2, 99.9% Bi2O3, 99.99% Nb2O5 are mixed in the following manner: 0.4 Li 0.05 Ce 0.05 )Bi 2.38 The mixture was weighed in the proportion shown in FIG. 1 , and a certain proportion of zirconium balls were added. The mixture was milled for 20 hours using a planetary ball mill. The medium used for the milling was anhydrous ethanol. The mixture was dried, pressed into a block, placed in an alumina crucible with a lid, and calcined in a muffle furnace at 850 ° C for 3 hours. After cooling, the mixture was taken out and crushed to obtain (Na 0.5-p-q A3 p A4 q )Bi i Nb2O9 ceramic powder.

[0080] Step 3: The ceramic powders pre-synthesized in Steps 1 and 2 were weighed at a molar ratio of 0.9:0.1 and placed in a ball mill. Zirconia balls and anhydrous ethanol were added in a certain proportion and ball milled for 20 hours. After ball milling, the slurry was dried at 60°C for 24 hours to obtain a powder with a median particle size (D50) of less than 2 microns. A 5% polyvinyl alcohol solution was added as a binder to the dried powder, and the powder was granulated and pressed to produce ceramic green sheets with a diameter of 8 mm.

[0081] Step 4: Place the ceramic green sheet obtained in step 3 into an electric furnace for debinding. The heating rate used for debinding is 5°C / min, the temperature is 600°C, and the holding time is 1 hour.

[0082] Step 5: Spread the debinded sample flat on an alumina or zirconia pad and place it in an atmosphere furnace to introduce oxygen for sintering. The oxygen flow rate is 0.8 L / min, the sintering heating rate is 5°C / min, the sintering temperature is 1120°C, and the holding time is 2 hours. After sintering, the ceramic material is cooled in the furnace. The powder X-ray diffraction results of the obtained ceramic material are as follows: Figure 2 The surface morphology of the obtained ceramic material is shown in Figure 3 shown.

[0083] Step 6: The oxygen-sintered ceramic material is double-sided polished and then ultrasonically cleaned. After cleaning, it is dried at 120°C and then printed with platinum slurry. The platinum electrodes are fired at 800°C for 30 minutes to ensure good ohmic contact between the ceramic and the electrodes.

[0084] Step 7: The prepared electrode ceramic material is subjected to the first polarization treatment in high-temperature silicone oil at a polarization temperature of 200°C, a polarization electric field of 150 kV / cm, and a polarization time of 30 minutes.

[0085] Step 8: Raise the temperature of the ceramic material after the first polarization to 500°C and keep it at this temperature for 24 hours to complete the first aging treatment.

[0086] Step 9: The ceramic material after the first aging is subjected to a second polarization treatment with the same polarity as the first polarization, the polarization temperature is 200°C, the polarization electric field is 200 kV / cm, and the polarization time is 30 minutes.

[0087] Step 10: The ceramic material after secondary polarization is subjected to a second aging process. The aging process is to first increase the temperature from room temperature to 600°C, keep the temperature for 24 hours, and then perform two heating and cooling cycles from 600°C to -60°C at a heating and cooling rate of 5°C / minute.

[0088] The aged ceramic material was subjected to quasi-static 33 Tester, impedance analyzer to test its piezoelectric coefficient d 33 , Planar electromechanical coupling coefficient k p , dielectric constant ε r , dielectric loss tanδ, the results are shown in Table 1. The resistivity of ceramic materials at different temperatures was tested using a Keithley 6517B high resistance meter. The results are shown in Table 1. Figure 4 shown.

[0089] Example 3

[0090] The bismuth-based composite high-temperature resistant piezoelectric ceramic material provided in this embodiment is:

[0091] 0.9[(Ca 0.9 Li 0.05 Sm 0.05 )Bi2Nb 1.98 W 0.02 O9]-0.1[Bi 0.35 Pb 0.65 Zn 0.175 Ti 0.825 O3] composite ceramics, wherein the subscript numbers represent the molar ratios of the elements.

[0092] A method for preparing a bismuth-based composite high-temperature resistant piezoelectric ceramic material comprises the following steps:

[0093] Step 1: 99% pure CaCO3, 99.9% Li2CO3, 99.99% Sm2O3, 99.9% Bi2O3, 99.99% Nb2O5, 99.9% WO3 are mixed in a sieve according to the following formula: 0.9 Li 0.05 Sm 0.05 )Bi2Nb 1.98 W 0.02 The mixture was weighed in the proportion shown in FIG09, and a certain proportion of zirconium balls was added. The mixture was milled for 20 hours using a planetary ball mill. The medium used for the milling was anhydrous ethanol. The mixture was dried, pressed into a block, placed in an alumina crucible with a lid, and calcined in a muffle furnace at 800°C for 4 hours. After cooling, the mixture was taken out and crushed to obtain Ca 1-x-y (A1 x A2 y )Bi2(Nb) 2-m-n (B1 m B2 n )O9 ceramic powder.

[0094] Step 2: Bi2O3 with a purity of 99.9%, PbO with a purity of 99.9%, ZnO with a purity of 99.9%, and TiO2 with a purity of 99.9%. 0.35 Pb 0.65 Zn 0.175 Ti 0.825 The mixture was weighed in the proportion shown in FIG3, and a certain proportion of zirconium balls was added. The mixture was milled for 16 hours using a planetary ball mill. The medium used for the milling was anhydrous ethanol. After the mixture was dried, it was pressed into a block, placed in an alumina crucible with a lid, and placed in a muffle furnace to calcine at 800°C for 6 hours. After cooling, it was taken out and crushed to obtain Bi a Pb 1- a Zn 0.5a Ti 1-0.5a O3 ceramic powder.

[0095] Step 3: The ceramic powders pre-synthesized in Steps 1 and 2 were weighed at a molar ratio of 0.9:0.1 and placed in a ball mill. Zirconia balls and anhydrous ethanol were added in a certain proportion and ball milled for 20 hours. After ball milling, the slurry was dried at 60°C for 24 hours to obtain a powder with a median particle size (D50) of less than 2 microns. A 5% polyvinyl alcohol solution was added to the dried powder as a binder, and the powder was granulated and pressed to produce ceramic green sheets with a diameter of 8 mm.

[0096] Step 4: Place the ceramic green sheet obtained in step 3 into an electric furnace for debinding treatment. The heating rate used for debinding is 5°C / min, the temperature is 600°C, and the holding time is 1 hour.

[0097] Step 5: Spread the debinded sample flat on an alumina or zirconia pad and place it in an atmosphere furnace to sinter with oxygen. The oxygen flow rate is 0.8 L / min, the sintering heating rate is 5 ℃ / min, the sintering temperature is 1120 ℃, and the holding time is 2 hours. After sintering, the ceramic material is cooled in the furnace. The powder X-ray diffraction results of the obtained ceramic material are as follows: Figure 2 The surface morphology of the obtained ceramic material is shown in Figure 3 shown.

[0098] Step 6: The oxygen-sintered ceramic material is double-sided polished and then ultrasonically cleaned. After cleaning, it is dried at 120°C and then printed with platinum slurry. The platinum electrodes are fired at 800°C for 30 minutes to ensure good ohmic contact between the ceramic and the electrodes.

[0099] Step 7: The ceramic material of the prepared electrode is subjected to the first polarization treatment in high-temperature silicone oil at a polarization temperature of 200° C., a polarization electric field of 130 kV / cm, and a polarization time of 30 minutes.

[0100] Step 8: Raise the temperature of the ceramic material after the first polarization to 500° C. and keep it at this temperature for 24 hours to complete the first aging treatment.

[0101] Step 9: The ceramic material after the first aging is subjected to a second polarization treatment according to the same polarity as the first polarization, with a polarization temperature of 200°C, a polarization electric field of 150 kV / cm, and a polarization time of 30 minutes.

[0102] Step 10: The ceramic material after secondary polarization is subjected to a second aging process. The aging process is to first increase the temperature from room temperature to 600°C, keep the temperature for 24 hours, and then perform two heating and cooling cycles from 600°C to -60°C at a heating and cooling rate of 5°C / minute.

[0103] The aged ceramic material was subjected to quasi-static 33 Tester, impedance analyzer to test its piezoelectric coefficient d 33 , Planar electromechanical coupling coefficient k p , dielectric constant ε r , dielectric loss tanδ, the results are shown in Table 1. The resistivity of ceramic materials at different temperatures was tested using a Keithley 6517B high resistance meter. The results are shown in Table 1. Figure 4 shown.

[0104] Figure 2 The XRD patterns show that the main phase of the ceramic material obtained in the present invention is a double-layer bismuth layered structure.

[0105] Figure 3 The results show that the resulting ceramic grains exhibit a significant lamellar morphology, indicating significant anisotropy in growth, as the growth rate of the grains perpendicular to the c-axis is significantly greater than that along the c-axis. Furthermore, the ceramic samples exhibit well-developed grains and high density.

[0106] Figure 4 The results show that the high temperature resistivity of the composite ceramic material is low, and the resistivity of the ceramic at 500 ℃ is greater than 10 6 Ωcm. That is, the oxygen vacancies in the CaBi2Nb2O9-based bismuth layered piezoelectric ceramic material were effectively reduced through the composite ceramic method, and a ceramic material with good application prospects in the field of high-temperature piezoelectricity was obtained.

[0107] Table 1 shows the room temperature piezoelectric coefficients d of the high temperature piezoelectric ceramics prepared in Examples 1 to 3. 33 , Planar electromechanical coupling coefficient k p , dielectric constant ε r , dielectric loss tanδ, and the performance of the ceramic material after being heated at 500 °C for 30 minutes and then cooled to room temperature.

[0108] Table 1

[0109]

[0110] Table 1 shows that the resulting composite ceramic material exhibits excellent piezoelectric properties, a high dielectric constant, and low dielectric loss at room temperature. Furthermore, after heat treatment at 500°C for 30 minutes, the change in both piezoelectric and dielectric properties is less than 1%. This demonstrates that the composite ceramic material obtained through the combination of secondary polarization, secondary aging, and thermal cycling has excellent high-temperature stability. Therefore, piezoelectric devices based on this composite material have promising application prospects at temperatures of 500°C and even higher.

[0111] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A bismuth-based composite high-temperature resistant piezoelectric ceramic material, characterized in that: The bismuth-based composite high-temperature resistant piezoelectric ceramic material is composed of a bismuth layered piezoelectric ceramic Ca 1-x-y (A1 x A2 y )Bi2(Nb) 2-m-n (B1 m B2 n )O9 and bismuth-based high-temperature piezoelectric ceramic material M composite composition; A1 is Li, A2 is Nd or Sm, B1 is Mn, and B2 is W; wherein: x is 0.04 or 0.05; y is 0.04 or 0.05; m is 0.0025 or 0; and n is 0.0075 or 0.02; The bismuth-based high-temperature piezoelectric ceramic material M is a bismuth layered piezoelectric ceramic (Na 0.5-p-q A3 p A4 q )Bi i Nb2O9 or Bi a Pb 1-a Zn 0.5a Ti 1-0.5a O3; A3 is alkali metal Li, A4 is Ce; p is 0.05; q is 0.05; i is 2.38; a is 0.35; The general chemical formula of the bismuth-based composite high-temperature resistant piezoelectric ceramic material is: z1[Ca 1-x-y (A1 x A2 y )Bi2(Nb) 2-m-n (B1 m B2 n )O9]-(1 - z1)[(Na 0.5-p-q A3 p A4 q )Bi i Nb2O9] or z2[Ca 1-x-y (A1 x A2 y )Bi2(Nb) 2-m-n (B1 m B2 n )O9]-(1-z2)[Bi a Pb 1-a Zn 0.5a Ti 1-0.5a O3], wherein z1 is 0.1 or 0.2; z2 is 0.

9.

2. The bismuth-based composite high-temperature resistant piezoelectric ceramic material according to claim 1, characterized in that: The bismuth-based composite high-temperature resistant piezoelectric ceramic material has a piezoelectric coefficient of (15-30) pC / N at room temperature, a room-temperature dielectric constant of 100-160 at 1 kHz, a room-temperature dielectric loss of 0.002-0.01 at 1 kHz, and a resistivity of (10 5 ~10 8 ) Ωcm; the change rate of the dielectric constant, dielectric loss and piezoelectric coefficient of the bismuth-based composite high-temperature resistant piezoelectric ceramic material after 500 ℃ insulation treatment is less than 1%.

3. The method for preparing a bismuth-based composite high-temperature resistant piezoelectric ceramic material according to claim 1, characterized in that: The following steps are involved: Step 1: Prefabricate Ca 1-x-y (A1 x A2 y )Bi2(Nb) 2-m-n (B1 m B2 n ) O9 ceramic powder: using various metal oxides, carbonates or nitrates as raw materials according to the chemical formula ratio, weighing, mixing, ball milling, drying, briquetting, calcining and crushing to obtain a pre-synthesized powder; Step 2, Prefabrication (Na 0.5-p-q A3 p A4 q )Bi i Nb2O9 ceramic powder or Bi a Pb 1-a Zn 0.5a Ti 1-0.5a O3 ceramic powder: using various metal oxides, carbonates or nitrates as raw materials according to the chemical formula ratio, weighing, mixing, ball milling, drying, briquetting, calcining and crushing to obtain pre-synthesized ceramic powder; Step 3: The ceramic powders pre-synthesized in Steps 1 and 2 are weighed in a molar ratio of z:(1-z), ball-milled, and dried to obtain a powder having a median particle size D50 of 1 to 2 μm. A binder is added to the powder, and the powder is granulated and pressed to obtain a ceramic green sheet; Step 4: Debinding the ceramic green sheet obtained in step 3 to obtain an intermediate product; Step 5: Spread the intermediate product on a pad and place it in an atmosphere furnace to introduce oxygen for sintering. The oxygen flow rate is 0.6-1.0 L / min, the sintering heating rate is 2-10 °C / min, the sintering temperature is 1050-1200 °C, and the holding time is 1-4 hours. After sintering, cool it in the furnace to obtain a ceramic material. Step 6: Polish the ceramic material on both sides, clean it and dry the printed electrodes; Step 7: subjecting the prepared electrode ceramic material to a first polarization treatment; Step 8: performing a first aging treatment on the ceramic material after the first polarization; Step 9: subjecting the ceramic material after the first aging treatment to a second polarization treatment at the same polarity as the first polarization treatment, wherein the second polarization temperature is 160-220° C., the polarization electric field is 120-220 kV / cm, and the polarization time is 20-60 minutes; Step 10: The ceramic material after the secondary polarization is subjected to a second aging treatment. The second aging treatment is as follows: the ceramic material after the second polarization is heated from room temperature to 550-600°C, kept warm for 24-48 hours, and then subjected to 2-5 heating and cooling thermal cycles from the current temperature to -60°C, with a heating and cooling rate of 2-5°C / minute, to obtain a bismuth-based composite high-temperature resistant piezoelectric ceramic material.

4. The method for preparing a bismuth-based composite high-temperature resistant piezoelectric ceramic material according to claim 3, characterized in that: In step 5, the oxygen flow rate is 0.8 L / min, the sintering heating rate is 5° C. / min, and the sintering temperature is 1120° C.

5. The method for preparing a bismuth-based composite high-temperature resistant piezoelectric ceramic material according to claim 3, characterized in that: In step 6, when printing the electrode, the firing temperature of the electrode is 700-1000° C., and the holding time is 10-60 minutes.

6. The method for preparing a bismuth-based composite high-temperature resistant piezoelectric ceramic material according to claim 3, characterized in that: In step 7, the polarization temperature during the first polarization treatment is 160-220° C., the polarization electric field is 120-220 kV / cm, and the polarization time is 20-60 minutes.

7. The method for preparing a bismuth-based composite high-temperature resistant piezoelectric ceramic material according to claim 3, characterized in that: In step 8, the ceramic material after the first polarization is heated to 500-600° C., kept at this temperature for 24-48 hours, and then cooled to room temperature to complete the first aging treatment.

8. The method for preparing a bismuth-based composite high-temperature resistant piezoelectric ceramic material according to claim 3, characterized in that: In step 10, the second aging treatment is as follows: the ceramic material after the second polarization is heated from room temperature to 600°C, kept warm for 24 hours, and then subjected to two heating and cooling thermal cycles from 600°C to -60°C at a heating and cooling rate of 5°C / minute to obtain a bismuth-based composite high-temperature resistant piezoelectric ceramic material.

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