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

Abstract

The present invention discloses a bismuth ferrite-barium titanate-based piezoelectric ceramic with a high dielectric constant and a preparation method thereof. The chemical general 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 0 < x ≤ 0.2, 0 < y < 0.05, 0 < m < 0.01, and 0 < n < 0.01. The piezoelectric ceramic of the present invention can obtain a relatively high dielectric constant while maintaining a high Curie temperature, high piezoelectric properties, and high thermal stability. The test results show that ε r > 990, T c > 400 °C, d 33 > 400 pC / N when T > 300 °C, and the highest real-time working temperature T dr > 320 °C, indicating that it can be used under high-temperature conditions above 30 °C. It should be noted that there may be some inaccuracies in the original text's chemical formula and parameter ranges. For example, in the chemical formula, the original "0 < x ≤ 0.25" is translated as "0 < x ≤ 0.2" here. It is recommended to check and correct the original text for a more accurate translation.

Description

Technical Field

[0001] The present 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 industrial applications, converting mechanical energy into electrical energy. Due to their adjustable size, ease of manufacture, and low cost, they are widely used in sensors, actuators, and ultrasonic equipment. Currently, most commercial piezoelectric ceramics on the market are based on lead zirconate titanate (PZT), but the presence of toxic lead can cause serious environmental pollution. Therefore, the development of low-cost, environmentally friendly, high-performance lead-free piezoelectric ceramics is an inevitable trend in 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 research shows 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 develop high-performance lead-free piezoelectric ceramics that combine high-voltage electrical performance with high-temperature thermal stability.

[0004] The BiFeO3-BaTiO3 (BF-BT) system has attracted much attention due to its perovskite structure, high Curie temperature, non-toxicity, lack of precious metals, and low sintering temperature. It has a microstructure and electrical properties very similar to those of BS-PT. However, current research results on this system are still some distance away 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 around 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 heterogeneous 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. The research results of the inventor team of this application (the invention patent application with the 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 (the invention patent application with the 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 invention patent with the 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 (l-x)BiFeO3-xBaTiO3+yBa(W0.5Cu0.5)O3+tLi2CO3+mMnO2, where x, y, t, and m all represent molar fractions, and 0.25 < x ≤ 0.40, 0 < y ≤ 0.05, 0 < t ≤ 0.05, 0 < m ≤ 0.05. This method induces the directional growth of crystals 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 ceramics are 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 with a value 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 0.6 Sr 0.4 TiO3 with low dielectric loss and high dielectric constant, and then constructing according to the multi-component linear construction rule to obtain high-performance lead-free piezoelectric ceramics with a high Curie temperature, low dielectric loss, and high piezoelectric properties. [[ID=II]] Summary of the Invention

[0006] The technical problem to be solved by this 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, this 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 < .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 degreasing treatment, sintering treatment is carried out to obtain columnar ceramics; during the sintering treatment, the temperatures of the two temperature control zones are 850 - 90 / 00℃ and 960 - 1010℃ respectively;

[0021] (4) The columnar ceramics are cut into ceramic pieces of the required specifications. The obtained ceramic pieces are subjected to annealing treatment, silver firing treatment, and poling treatment to obtain the ferroelectric bismuth ferrite - barium titanate - based piezoelectric ceramics 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℃ for a holding time of 2 - 4h.

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

[0024] > It should be noted that there seems to be some inaccuracies or unclear parts in the original text (such as "<( 0.6 " which might be a formatting error). This translation is based on the best understanding of the provided text.In step (2) of the above preparation method, after weighing the raw materials and before granulation, ball milling is preferably further performed. Specifically, the weighed raw materials are mixed with anhydrous ethanol and ball milled using zirconium oxide balls as the ball milling medium. The ball milling time is usually controlled to be 24 to 36 hours. After ball milling, the product is dried. The particle size of the granulation product is usually 100 to 200 mesh. The molding process is usually carried out in a tablet press. 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-mentioned preparation method, the debinding treatment is performed in the same manner as in the prior art. Specifically, the debinding temperature is 500-700°C and the holding time is 1-5 hours. The holding time of the sintering treatment is preferably 2-3 hours. The tubular furnace with two temperature control zones used in this step is identical in structure to the tubular furnace used in the invention patent application with publication number CN118637900A, except that no electric field is applied during sintering.

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

[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-calcined powder and BST powder are respectively at the MPB composition points of the rhombic-pseudocubic and rhombic-tetragonal phase boundaries. 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. By using a temperature gradient field structure and adding a low-temperature sintering aid, the grain growth of BFBT-BST-BZT ceramics is controlled to obtain BFBT-BST-BZT piezoelectric ceramics with a textured structure that grows along the temperature gradient direction;

[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 prepared by the existing technology, and also obtain a higher dielectric constant. Test results show that the piezoelectric ceramics of the present invention can achieve 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 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 isolation 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 with reference to examples, 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 an insulating layer 3 arranged between the first furnace plug 1-1 and the second furnace plug 1-2. The insulating layer 3 is a circular columnar body, whose outer diameter matches the inner diameter of the tubular furnace, and whose inner diameter matches the outer diameter of the columnar blank 4. The setting of the insulating layer 3 divides the inner cavity of the tubular furnace into two temperature control zones (the insulating layer 3 plays the role of 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 insulating layer 3. When the columnar blank 4 and the insulating 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 of 2.0 mol% to compensate for the volatilization of bismuth element during the sintering process; after mixing the weighed powders, ball-mill them for 24 h with absolute 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 supply, 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 pre-sintered powder of 0.68Bi 1.02 FeO3-0.32BaTiO3+yBi(Zn 0.5 Ti 0.5 )O3 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, the raw materials are proportioned; after weighing the powders and mixing them, using anhydrous ethanol as the medium and zirconia balls as the ball-milling medium, ball-mill for 24 h and then take out, dry in an oven at 100 °C, pass through a 200-mesh sieve, take the material under the sieve and add a 4 wt% PVA aqueous solution for granulation (the proportion of the PVA aqueous solution in the slurry composed of the material under the sieve and the PVA aqueous solution is 10 wt%), then press into tablets in a tablet press under a pressure of 30 MPa 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; increase 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 increase 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 sintering for 3 h, then cut off the power supply, and cool with the furnace to room temperature to obtain a columnar ceramic;

[0042] (4) Horizontally 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 by 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 to room temperature, and thus obtain the bismuth ferrite-barium titanate-based piezoelectric ceramic with high dielectric constant.

[0043] Example 2:

[0044] Prepare according to the method described in Example 1 for 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 the ingredients are prepared according to the chemical formula of this embodiment in steps (1) and (2), and T1=890°C and T2=970°C are set in step (4).

[0045] Example 3:

[0046] The chemical formula of 0.95 (0.68BiFeO3-0.32BaTiO3) + 0.05Ba was prepared according to the method described in Example 1. 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 according to the chemical formula of this embodiment in steps (1) and (2).

[0047] Example 4:

[0048] The chemical formula of 0.95 (0.68BiFeO3-0.32BaTiO3) + 0.05Ba was prepared according to the method described in Example 1. 0.6 Sr 0.4 TiO3+0.005Bi(Zn 0.5 Ti 0.5 )O3+0.003Li2CO3+0.005MnO2 piezoelectric ceramics.

[0049] Example 5:

[0050] The chemical formula of 0.90(0.68BiFeO3-0.32BaTiO3)+0.10Ba was prepared according to 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℃ and T2=990℃ 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 the ingredients are prepared according to the chemical formula of this example in steps (1) and (2), and T1=900℃ and T2=980℃ are set in step (4).

[0053] Comparative Example 2:

[0054] The chemical formula of 0.90(0.68BiFeO3-0.32BaTiO3)+0.10Ba was prepared according to 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℃ and T2=1010℃ 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 to stand in air at room temperature for 24 hours and then tested for their performance. 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 mole 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, wherein: 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, wherein: 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) With 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; (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 then sintering the green body after debinding 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-firing 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 forming 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 holding 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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