Bismuth ferrite-barium titanate based piezoelectric ceramic with high dielectric constant and preparation method thereof

Abstract

The invention discloses a bismuth ferrite-barium titanate based piezoelectric ceramic with a high dielectric constant and a preparation method thereof, and the chemical general formula of the piezoelectric ceramic is [(1-x) (0.68 Bi < 1.02 > FeO < 3 >-0.32 BaTiO3) + xBa < 0.6 > Sr < 0.4 > TiO3] + yBi (Zn < 0.5 > Ti < 0.5 >) O < 3 + > m Li < 2 > CO < 3 + > n MnO < 2, 0 lt >, x is less than or equal to 0.25, 0lt; yt; Yt; 0.05, 0 lt; mlt; mlt; 0.01, 0 lt; nlt; and 0.01%. The piezoelectric ceramic keeps high Curie temperature, high piezoelectric performance and high thermal stability, and can obtain a high dielectric constant. Test results show that: epsilon rgt; 990, Tcgt, 990, Tcgt; 400 DEG C, at Tgt; d is 33gt at the temperature of 300 DEG C; the temperature is 400 pC / N, and the maximum real-time working temperature is Tdrgt; and the temperature is 320 DEG C, so that the material can be used under the high-temperature condition of 300 DEG C or above.

Description

Technical Field

[0001] The invention relates to the technical field of piezoelectric ceramics, and in particular to a bismuth ferrite-barium titanate-based piezoelectric ceramic with a high dielectric constant and a preparation method thereof. Background Art

[0002] Piezoelectric ceramics have important applications in the industrial field. They can convert mechanical energy and electrical energy into each other. Due to their adjustable size, easy manufacturing, and low price, they are widely used in sensors, actuators, and ultrasonic equipment. At present, most of the commercial piezoelectric ceramics on the market are based on lead zirconate titanate (PZT), but because they contain toxic lead, they will cause serious environmental pollution problems. Therefore, the development of low-cost, environmentally friendly, high-performance lead-free piezoelectric ceramics is an inevitable trend for future development.

[0003] With the continuous development of science and technology, the application of high-temperature piezoelectric materials is becoming more and more extensive. They are widely used in aerospace, automobiles, oil exploration, 3D printing, ultrasonic medical treatment and other fields. However, existing studies have shown that the high-temperature stability and high-voltage electrical properties of piezoelectric ceramics are somewhat contradictory, that is, the higher the piezoelectric performance, the lower the temperature stability, and the higher the Curie temperature, the lower the piezoelectric performance. But there are exceptions. The bismuth scandate-lead titanate (BiScO3-PbTiO3, BS-PT) system (Curie temperature (T c )>450℃, in-situ depolarization temperature (T dr )>400℃, piezoelectric constant (d 33 )>450pC / N). However, the high price of scandium metal and the toxicity of lead severely limit its application. Therefore, it is of great significance to study and obtain high-performance lead-free piezoelectric ceramics with both high voltage electrical properties and high temperature thermal stability.

[0004] The BiFeO3-BaTiO3 (BF-BT) system has attracted much attention due to its perovskite structure system, high Curie temperature, non-toxicity, lack of precious metals, and low sintering temperature. It has a microstructure and electrical properties very similar to BS-PT. However, the current research results of this system are still a long way from practical application. Its main problems are low dielectric constant, high dielectric loss, and low room temperature piezoelectric performance. Zuo Ruzhong (J. Mater. Chem. C, 2022, 10, 8301–8309) of Anhui University has improved the maximum room temperature piezoelectric performance to about 210pC / N by constructing a quaternary system of bismuth ferrite-barium titanate-bismuth sodium titanate-bismuth magnesium niobate (BF-BT-BNT-BMN). Liu Laijun et al. from Guilin University of Technology (J. Mater. Chem. C, 2022, 10, 8301) prepared bismuth ferrite-barium titanate-bismuth potassium titanate (BF-BT-BKT) ceramics through high-temperature quenching and other processes, and obtained room temperature piezoelectric performance of 150pC / N and non-in-situ depolarization temperature (T d ) Ceramic samples reaching 570°C, however, the high-temperature quenching process easily forms a large number of microcracks in the ceramics, which are prone to aging during use, and the quenching process is extremely easy to damage the equipment. The operation is complicated and not suitable for industrial production. In order to reduce the dielectric loss of the system, the team of Wu Jiagang and Zheng Ting from Sichuan University (Journal of Alloys and Compounds 1006(2024)176295) adopted the method of adding inhomogeneous Mn to block the BF-BT defect carriers, which effectively improved the resistivity of the ceramics. However, the defects of high dielectric loss and low dielectric constant of the BF-BT system still cannot be effectively solved.

[0005] Barium strontium titanate (Ba 0.6 Sr 0.4 TiO3, abbreviated as BST) has a high dielectric constant and low dielectric loss, and is the main material for making high dielectric constant capacitors. BF-BT ceramics have a low dielectric constant (100<ε r <500), the loss is high. It is known in the art that the thermal stability of piezoelectric ceramics is not only related to the Curie temperature, but also to the phase structure. The higher the tetragonality, the higher the temperature stability. 0.5 Ti 0.5)O3 (abbreviated as BZT) is a perovskite-structured ceramic with the highest known Curie temperature and the strongest tetragonality currently. The research results of the inventor team of this application (a patent application with publication number CN110128126A) show that introducing BZT and bismuth aluminate (BiAlO3) into BF-BT ceramics to form a solid solution can improve the thermal stability of this system. On the other hand, the piezoelectric properties of piezoelectric ceramics are also closely related to the microstructure of the ceramics. The inventor team of this application found in previous research (a patent application with publication number CN118637900A) that by constructing a certain temperature gradient field and electric field, the grain growth shows a certain direction selectivity, which can greatly increase the piezoelectric properties. In the patent with publication number CN118637900A, a texture preparation method of bismuth ferrite-barium titanate lead-free piezoelectric ceramics with both high piezoelectric properties and thermal stability is disclosed. The chemical composition general formula of this piezoelectric ceramic is (1-x)BiFeO3-xBaTiO3+yBa(W0.5Cu0.5)O3+tLi2CO3+mMnO2, where x, y, t, and m all represent mole fractions, and 0.25 < x ≤ 0.40, 0 < y ≤ 0.05, 0 < t ≤ 0.05, 0 < m ≤ 0.05. This method induces crystal orientation growth and affects the domain structure distribution by adding a temperature gradient field and an external electric field during the sintering stage, and the sintered cylindrical ceramic is transversely cut, longitudinally cut, and obliquely cut with a laser to obtain the in-situ depolarization temperature T dr greater than 300 °C, high-temperature piezoelectric constant d 33 textured lead-free piezoelectric ceramics higher than 600 pC / N, but the dielectric constant of the piezoelectric ceramics prepared by this method is relatively low (ε r = 180 - 500). To solve the above deficiency of low dielectric constant, the inventor team of this application proposed this application, by introducing SrTiO3 with low dielectric loss to form Ba with low dielectric loss and high dielectric constant with BaTiO3 0.6 Sr 0.4 TiO3, and then constructing according to the multi-component linear construction rule to obtain high-performance lead-free piezoelectric ceramics with high Curie temperature, low dielectric loss, and high piezoelectric properties. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a bismuth ferrite-barium titanate-based piezoelectric ceramic with a high dielectric constant and a preparation method thereof, which has a significant improvement in dielectric constant on the premise of maintaining a high Curie temperature, high piezoelectric properties, and high thermal stability.

[0007] To solve the above technical problems, the present invention adopts the following technical solutions:

[0008] A bismuth ferrite-barium titanate-based piezoelectric ceramic with a high dielectric constant, the chemical general formula of this piezoelectric ceramic is [(1-x)(0.68Bi1.02 (FeO3 - 0.32BaTiO3) + xBa 0.6 Sr 0.4 TiO3] + yBi(Zn 0.5 Ti 0.5 )O3 + mLi2CO3 + nMnO2, where x, y, m, and n represent the molar fractions of the components, 0 < x ≤ 0.25, 0 < y < 0.05, 0 < m < 0.01, 0 < n < 0.01.

[0009] The present invention uses the BF - BT system as the matrix material. On the basis of introducing BZT to increase the tetragonality of the ceramic and improve the thermal stability of the ceramic, by designing a specific multi - component and multi - phase co - existence structure, the system affects the grain growth direction only under the condition of sintering in a temperature gradient field, so that the obtained ceramic effectively improves its dielectric constant while maintaining a high Curie temperature, high piezoelectric properties, and high thermal stability.

[0010] Furthermore, the selection of x, y, m, and n is preferably: 0 < x ≤ 0.10, 0 < y ≤ 0.03, 0 < m ≤ 0.005, 0 < n ≤ 0.05; more preferably, x = 0.025, 0.05 or 0.10, y = 0.005, 0.015 or x = 0.025, m = 0.003, n = 0.005.

[0011] In some preferred embodiments, the selection of x, y, m, and n is specifically:

[0012] x = 0.05, y = 0.025, m = 0.003, n = 0.005; or

[0013] x = 0.025, y = 0.025, m = 0.003, n = 0.005; or

[0014] x = 0.05, y = 0.015, m = 0.003, n = 0.005; or

[0015] x = 0.05, y = 0.005, m = 0.003, n = 0.005; or

[0016] x = 0.10, y = 0.025, m = 0.003, n = 0.005.

[0017] The preparation method of the bismuth ferrite - barium titanate - based piezoelectric ceramic with high dielectric constant according to the present invention includes the following steps:

[0018] (1) Using Bi2O3, Fe2O3, BaCO3, TiO2, and ZnO as raw materials, according to 0.68Bi 1.02 (FeO3 - 0.32BaTiO3) + yBi(Zn 0.5 Ti0.5 ) O3, with a ratio of 0 < y < 0.05 for batching, followed by pre-sintering to obtain 0.68Bi 1.02 FeO3 - 0.32BaTiO3 + yBi(Zn 0.5 Ti 0.5 )O3 pre-sintered powder;

[0019] (2) Using 0.68Bi 1.02 FeO3 - 0.32BaTiO3 + yBi(Zn 0.5 Ti 0.5 )O3 pre-sintered powder, Ba 0.6 Sr 0.4 TiO3, Li2CO3 and MnO2 as raw materials, according to the ratio of [(1 - x)(0.68Bi 1.02 FeO3 - 0.32BaTiO3) + xBa 0.6 Sr 0.4 TiO3] + yBi(Zn 0.5 Ti 0.5 )O3 + mLi2CO3 + nMnO2, where 0 < x ≤ 0.25, 0 < y < 0.05, 0 < m < 0.01, 0 < n < 0.01 for batching. The obtained mixed powder is granulated and formed to obtain a columnar green body;

[0020] (3) The obtained columnar green body is placed in a tubular furnace with two temperature control zones, such that the two ends of the columnar green body are respectively in the two temperature control zones. After debinding treatment, sintering treatment is carried out to obtain a columnar ceramic; during the sintering treatment, the temperatures of the two temperature control zones are 850 - 900 °C and 960 - 1010 °C respectively;

[0021] (4) The columnar ceramic is cut into ceramic pieces of the required specifications. The obtained ceramic pieces are subjected to annealing treatment, silver firing treatment and poling treatment, thereby obtaining the bismuth ferrite - barium titanate - based piezoelectric ceramic with high dielectric constant.

[0022] In step (1) of the above preparation method, the operations of batching and pre-sintering are the same as the existing conventional operations. Specifically, during batching, the Bi element is preferably in an excess of 2.0 mol% to compensate for the volatilization of bismuth element during high-temperature sintering. After weighing all the raw materials, wet ball milling and powder mixing can be carried out first, followed by drying and then pre-sintering. The pre-sintering is preferably carried out at 750 - 800 °C for a holding time of 2 - 4 h.

[0023] In step (2) of the above preparation method, the selection of x, y, m and n is as described above.

[0024] In step (2) of the above preparation method, after weighing each raw material and before granulation, preferably also includes ball milling, specifically, the weighed raw materials are mixed with anhydrous ethanol, and ball milling is performed using zirconium oxide balls as ball milling media. The ball milling time is usually controlled to be 24 to 36 hours, and the ball milling is dried after completion. The particle size of the product after granulation is usually 100 to 200 meshes. The molding process is usually carried out in a tablet press, and the molding pressure is preferably 30 to 40 MPa. The diameter of the columnar blank after molding is 10 to 12 mm and the height is 14 to 16 mm.

[0025] In step (3) of the above preparation method, the operation of the debinding treatment is the same as that of the prior art, specifically, the temperature during the debinding treatment is 500-700°C, and the holding time is 1-5 hours; the holding time of the sintering treatment is preferably 2-3 hours. In this step, the tubular furnace with two temperature control zones is the same as the tubular furnace used in the invention patent application with publication number CN118637900A, except that no electric field is required during sintering.

[0026] In step (4) of the above preparation method, the operations of annealing, silver burning and polarization are the same as those in the prior art. Specifically, the annealing is carried out at 850-950°C for 20-30 min; the silver burning is carried out at 500-600°C for 20-30 min; the polarization is carried out in silicone oil with a polarization electric field of 6000 V / mm, a polarization temperature of 100-120°C and a time of 10-30 min.

[0027] Compared with the prior art, the present invention is characterized in that:

[0028] 1.Single synthesis of 0.68Bi 1.02 FeO3-0.32BaTiO3+yBi(Zn 0.5 Ti 0.5 )O3 pre-sintered powder to make 0.68Bi 1.02 FeO3-0.32BaTiO3+yBi(Zn 0.5 Ti 0.5 )O3 pre-sintered powder and BST powder are at the MPB composition points of the rhombic-pseudo-cubic and rhombic-tetragonal phase boundaries, respectively. Then, according to the multi-component linear combination law, (1-x)BFBT-xBST multiphase coexistence BFBT-BST ceramics are constructed to achieve the goal of improving the dielectric constant of the ceramics while maintaining higher piezoelectric properties.

[0029] 2. Use trace amounts of BZT to regulate the phase structure of BFBT-BST ceramics, and obtain BFBT-BST-BZT phase structure ceramics close to the tetragonal phase near the multi-phase coexistence point, thereby improving the thermal stability of the ceramics by improving the tetragonality of the ceramics.

[0030] 3. Using temperature gradient field construction and adding low-temperature sintering aids to control the grain growth of BFBT-BST-BZT ceramics, BFBT-BST-BZT piezoelectric ceramics with a textured structure that grows along the temperature gradient direction are obtained;

[0031] 4. Through the combination of the above composition and structure control technology, the prepared BFBT-BST-BZT ceramics have the high Curie temperature, high piezoelectric performance and high thermal stability of the ceramics of this system prepared by the existing technology, and also obtain a higher dielectric constant. The test results show that the piezoelectric ceramics of the present invention have the following properties: room temperature dielectric constant ε r >990, Curie temperature T c >400℃, when T>300℃d 33 >400pC / N, maximum real-time operating temperature T dr >320℃, the above data show that it can be used under high temperature conditions above 300℃. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of the principle of applying a temperature gradient field during the sintering process of the bismuth ferrite-barium titanate-based piezoelectric ceramic sample with a high dielectric constant described in the present invention.

[0033] The numbers in the figure are:

[0034] 1-1 first furnace plug, 1-2 second furnace plug, 1-3 first temperature zone, 1-4 second temperature zone, 3 partition layer, 4 columnar blank. DETAILED DESCRIPTION

[0035] In order to better explain the technical solution of the present invention, the present invention is further described in detail below in conjunction with embodiments, but the embodiments of the present invention are not limited thereto.

[0036] The tubular furnace with two temperature control zones used in the following examples is as follows: Figure 1As shown in the figure, it is a two-temperature-zone tubular furnace, including a first furnace plug 1-1 and a second furnace plug 1-2 arranged at both ends of the furnace body, and a partition layer 3 arranged between the first furnace plug 1-1 and the second furnace plug 1-2. The partition layer 3 is a circular columnar body, the outer diameter of which matches the inner diameter of the tubular furnace, and the inner diameter of which matches the outer diameter of the columnar blank 4. The setting of the partition layer 3 divides the inner cavity of the tubular furnace into two temperature control zones (the partition layer 3 plays a role in isolating the two temperature control zones and maintaining the temperature gradient (temperature difference) at both ends of the columnar blank 4), that is, the first temperature control zone 1-3 and the second temperature control zone 1-4. The formed columnar blank 4 is placed in the hollow through hole of the partition layer 3. When the columnar blank 4 and the partition layer 3 are placed in the middle of the inner cavity of the furnace body, both ends of the columnar blank 4 are respectively in the first temperature control zone 1-3 and the second temperature control zone 1-4.

[0037] Example 1:

[0038] Prepare a piezoelectric ceramic with the chemical formula 0.95(0.68BiFeO3-0.32BaTiO3)+0.05Ba 0.6 Sr 0.4 TiO3+0.025Bi(Zn 0.5 Ti 0.5 )O3+0.003Li2CO3+0.005MnO2.

[0039] (1) Using analytical pure Bi2O3, Fe2O3, BaCO3, TiO2, ZnO as raw materials, with a ratio of 0.68Bi 1.02 FeO3-0.32BaTiO3+yBi(Zn 0.5 Ti 0.5 )O3, where 0 < y < 0.05 for batching. When batching, the Bi element is in excess by 2.0 mol% to make up for the volatilization of bismuth element during sintering; after mixing the weighed powders, ball-mill them for 24 h with anhydrous ethanol as the medium, then take them out, dry them in an oven at 100 °C, pass through a 200-mesh sieve, and then put the sifted material into a high-alumina crucible, compact it, cover it, and place it in a muffle furnace. Rapidly heat it to 760 °C at a heating rate of 300 °C / h, keep it warm for 4 h, then cut off the power and cool it with the furnace to obtain the pre-sintered powder of 0.68Bi 1.02 FeO3-0.32BaTiO3+yBi(Zn 0.5 Ti 0.5 )O3;

[0040] (2) Using the 0.68Bi 1.02 FeO3-0.32BaTiO3+yBi(Zn 0.5 Ti 0.5 )O3 pre-sintered powder obtained in step (1), Ba 0.6 Sr 0.4Using TiO3, Li2CO3 and MnO2 as raw materials, according to the formula [(1 - x)(0.68Bi 1.02 FeO3 - 0.32BaTiO3)+xBa 0.6 Sr 0.4 TiO3]+yBi(Zn 0.5 Ti 0.5 )O3+mLi2CO3+nMnO2, where 0 < x ≤ 0.25, 0 < y < 0.05, 0 < m < 0.01, 0 < n < 0.01, weigh the raw materials; mix the weighed powders, use anhydrous ethanol as the medium and zirconia balls as the ball - milling medium, ball - mill for 24 h and then take out, dry at 100 °C in a drying oven, pass through a 200 - mesh sieve, take the undersize material, add a 4 wt% aqueous PVA solution for granulation (the proportion of the PVA aqueous solution in the slurry composed of the undersize material and the PVA aqueous solution is 10 wt%), then press - mold at a pressure of 30 MPa in a tablet press to obtain a columnar green body with a diameter of 11.0 mm and a height of 15.0 mm;

[0041] (3) Place the obtained columnar green body in the Figure 1 shown tubular furnace, make the two ends of the columnar green body be in two temperature - control zones respectively, set the temperature of the first temperature - control zone (T1) to 900 °C and the temperature of the second temperature - control zone (T2) to 970 °C; raise the furnace temperature to 600 °C at a heating rate of 60 °C / h and keep it for 4 h to remove the binder; then raise the temperatures of the two temperature - control zones to T1 = 900 °C and T2 = 970 °C at a heating rate of 5 °C / min, keep it for 3 h for sintering, then cut off the power supply and cool down to room temperature with the furnace to obtain a columnar ceramic;

[0042] (4) Transversely cut the sintered columnar ceramic along the direction perpendicular to the cylinder length, the cut sample is coin - shaped, with a thickness of 1.0 mm and a diameter of 10.0 mm; polish the surface of the cut sample smoothly, then place it in a muffle furnace for annealing treatment at 900 °C for 30 min to eliminate the internal stress of the ceramic; coat the surfaces at both ends of the sample obtained from the annealing treatment with silver paste and burn the silver at 550 °C for 30 min; place the sample after burning the silver in silicone oil for polarization, control the polarization electric field to be 6000 V / mm, the polarization temperature to be 120 °C, and the time to be 15 min, keep the polarization electric field, take it out after cooling down to room temperature, and thus obtain the bismuth ferrite - barium titanate - based piezoelectric ceramic with high dielectric constant.

[0043] Example 2:

[0044] Prepare the piezoelectric ceramic with the chemical formula 0.975(0.68BiFeO3 - 0.32BaTiO3)+0.025Ba 0.6 Sr 0.4 TiO3+0.025Bi(Zn 0.5 Ti0.5 )O3+0.003Li2CO3+0.005MnO2, except that in steps (1) and (2), the ingredients are prepared according to the chemical formula of this embodiment, and in step (4), T1=890°C and T2=970°C are set.

[0045] Embodiment 3:

[0046] Prepare the product with the chemical formula of 0.95(0.68BiFeO3-0.32BaTiO3)+0.05Ba 0.6 Sr 0.4 TiO3+0.015Bi(Zn 0.5 Ti 0.5 )O3+0.003Li2CO3+0.005MnO2, except that the ingredients are prepared in steps (1) and (2) according to the chemical formula of this embodiment.

[0047] Embodiment 4:

[0048] Prepare the product with the chemical formula of 0.95(0.68BiFeO3-0.32BaTiO3)+0.05Ba 0.6 Sr 0.4 TiO3+0.005Bi(Zn 0.5 Ti 0.5 )O3+0.003Li2CO3+0.005MnO2 piezoelectric ceramics.

[0049] Embodiment 5:

[0050] Prepare the compound of formula 0.90(0.68BiFeO3-0.32BaTiO3)+0.10Ba by the method described in Example 1. 0.6 Sr 0.4 TiO3+0.025Bi(Zn 0.5 Ti 0.5 )O3+0.003Li2CO3+0.005MnO2, except that in steps (1) and (2), the ingredients are prepared according to the chemical formula of this embodiment, and in step (4), T1=900°C and T2=990°C are set.

[0051] Comparative Example 1:

[0052] According to the method described in Example 1, a 0.68BiFeO3-0.32BaTiO3+0.025Bi(Zn 0.5 Ti 0.5)O3+0.003Li2CO3+0.005MnO2, except that in steps (1) and (2), the ingredients are prepared according to the chemical formula of this example, and in step (4), T1=900°C and T2=980°C are set.

[0053] Comparative Example 2:

[0054] Prepare the compound of formula 0.90(0.68BiFeO3-0.32BaTiO3)+0.10Ba by the method described in Example 1. 0.6 Sr 0.4 The piezoelectric ceramic of TiO3+0.003Li2CO3+0.005MnO2 is different in that the ingredients are prepared according to the chemical formula of this example in steps (1) and (2), and T1=920°C and T2=1010°C are set in step (4).

[0055] The bismuth ferrite-barium titanate-based piezoelectric ceramics with high dielectric constants prepared in Examples 1 to 5 and Comparative Examples 1 to 2 were left standing in air at room temperature for 24 hours and their performance was tested. The results are shown in Table 1 below.

[0056] Table 1:

[0057]

[0058]

Claims

1. A bismuth ferrite-barium titanate-based piezoelectric ceramic with a high dielectric constant, characterized in that: The chemical formula of the piezoelectric ceramic is [(1-x)(0.68Bi 1.02 FeO3-0.32BaTiO3)+xBa 0.6 Sr 0.4 TiO3]+yBi(Zn 0.5 Ti 0.5 )O3+mLi2CO3+nMnO2, where x, y, m and n represent the molar fractions of the components, 0 <x≤0.25,0<y<0.05,0<m<0.01,0<n<0.01。 2. The bismuth ferrite-barium titanate-based piezoelectric ceramic with a high dielectric constant according to claim 1, characterized in that: 0 <x≤0.10,0<y≤0.03,0<m≤0.005,0<n≤0.05。 3. The bismuth ferrite-barium titanate-based piezoelectric ceramic with a high dielectric constant according to claim 1, characterized in that: x=0.025, 0.05 or 0.10, y=0.005, 0.015 or 0.025, m=0.003, n=0.

005.

4. The method for preparing the bismuth ferrite-barium titanate-based piezoelectric ceramic with a high dielectric constant according to claim 1, comprising the following steps: (1) Using Bi2O3, Fe2O3, BaCO3, TiO2 and ZnO as raw materials, after proportioning according to the ratio of 0.68Bi 1.02 FeO3 - 0.32BaTiO3 + yBi(Zn 0.5 Ti 0.5 )O3, where 0 < y < 0.05, and then pre - sintering, 0.68Bi 1.02 FeO3 - 0.32BaTiO3 + yBi(Zn 0.5 Ti 0.5 )O3 pre - sintered powder is obtained; (2) Using 0.68Bi 1.02 FeO3 - 0.32BaTiO3 + yBi(Zn 0.5 Ti 0.5 )O3 pre - sintered powder, Ba 0.6 Sr 0.4 TiO3, Li2CO3 and MnO2 as raw materials, according to the formula [(1 - x)(0.68Bi 1.02 FeO3 - 0.32BaTiO3) + xBa 0.6 Sr 0.4 TiO3] + yBi(Zn 0.5 Ti 0.5 )O3 + mLi2CO3 + nMnO2, where 0 < x ≤ 0.25, 0 < y < 0.05, 0 < m < 0.01, 0 < n < 0.01 for batching. The obtained mixed powder is granulated and formed to obtain a columnar green body; (3) placing the obtained columnar green body in a tubular furnace with two temperature control zones, so that the two ends of the columnar green body are respectively in the two temperature control zones, and performing a sintering treatment after a binder removal treatment to obtain a columnar ceramic; during the sintering treatment, the temperatures of the two temperature control zones are 850-900° C. and 960-1010° C. respectively; (4) Cutting the columnar ceramic into ceramic sheets of required specifications, and subjecting the obtained ceramic sheets to annealing, silver sintering and polarization treatment to obtain the bismuth ferrite-barium titanate-based piezoelectric ceramics with a high dielectric constant.

5. The preparation method according to claim 4, characterized in that: In step (2), 0 <x≤0.10,0<y≤0.03,0<m≤0.005,0<n≤0.05。 6. The preparation method according to claim 4, characterized in that: In step (2), x=0.025, 0.05 or 0.10, y=0.005, 0.015 or 0.025, m=0.003, and n=0.

005.

7. The preparation method according to any one of claims 4 to 6, characterized in that: In step (1), pre-sintering is carried out at 750-800°C.

8. The preparation method according to any one of claims 4 to 6, characterized in that: In step (2), the diameter of the columnar blank after the molding process is 10 to 12 mm, and the height is 14 to 16 mm.

9. The preparation method according to any one of claims 4 to 6, characterized in that: In step (3), the temperature of the debinding treatment is 500-700° C., and the insulation time is 1-5 hours.

10. The preparation method according to any one of claims 4 to 6, characterized in that: In step (3), the holding time of the sintering treatment is 2 to 3 hours.

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