A high polarization lead-free perovskite ceramic material and preparation method

Abstract

The present invention discloses a highly polarized lead-free perovskite ceramic material and a preparation method thereof, which relates to the technical field of energy storage ceramic dielectric materials. Among them, the lead-free perovskite ceramic material is solid-solved by Bi 0.5 Na 0.5 TiO3 and Ba(Mg 0.5 W 0.5 )O3. In this application, by introducing Ba(Mg 0.5 W 0.5 )O3 into the Bi 0.5 Na 0.5 TiO3 lead-free relaxor ferroelectric ceramic, the prepared lead-free perovskite ceramic material has a smaller grain size, and the grain arrangement is relatively dense, with almost no voids appearing, and good densification; in addition, the lead-free perovskite ceramic material of this application is doped with Ba(Mg 0.5 W 0.5 )O3, which generates a large lattice distortion at the B site of the ceramic, and the induced saturation polarization intensity exceeds 90 uC / cm 2 .

Description

Technical Field

[0001] The present application relates to the technical field of energy storage ceramic dielectric materials, and in particular to a highly polarized lead-free perovskite ceramic material and a preparation method thereof. Background Art

[0002] Lead-free perovskite ceramic materials have become a key research direction in the field of energy storage ceramic dielectric materials due to their green nature. 0.5 Na 0.5 TiO3) due to its A-site Bi 3+ The 6s orbital and O 2- The 2p orbital hybridization forms an asymmetric covalent bond, which makes it highly polar and has a high application prospect in the energy storage direction. In recent years, it has attracted the attention of many scientific researchers. However, pure BNT-based ceramics have problems such as high residual polarization intensity, low breakdown field strength, slow charge and discharge speed, and low energy storage efficiency. Therefore, it is necessary to study doped lead-free perovskite ceramic materials.

[0003] In the prior art, Chinese patent CN118851748A discloses an energy storage ceramic material and a preparation method thereof and a preparation method of a high energy storage density ceramic capacitor dielectric. The general formula of the energy storage ceramic material is (1-y)(Bi 0.5 Na 0.5 )A x DE3-yG, wherein D is Ti element and E is O element. This invention improves the stability of the structure and the performance of the material by constructing a quasi-isotropic phase boundary.

[0004] However, the saturation polarization intensity of the above-mentioned prior art ceramic material decreases after doping, and with the increase of doping concentration, the saturation polarization intensity cannot be maintained in a relatively high range, which limits the further improvement of material performance. Summary of the invention

[0005] The present application provides a high-polarization lead-free perovskite ceramic material and a preparation method, which are used to solve the problem of reduced saturation polarization intensity after doping in existing energy storage ceramic dielectric material technology.

[0006] On the one hand, the present application provides a highly polarized lead-free perovskite ceramic material, comprising Bi 0.5 Na 0.5 TiO3 and Ba(Mg 0.5 W 0.5 )O3 solid solution.

[0007] On the other hand, the present application provides a method for preparing a highly polarized lead-free perovskite ceramic material, comprising the following steps:

[0008] Step 1: Mix MgO and WO3 to obtain a first mixture, and sinter the first mixture to obtain a compound MgWO4.

[0009] Step 2: Mix Bi2O3, Na2CO3, TiO2, BaCO3 and the compound MgWO4 obtained in step 1 to obtain a second mixture.

[0010] Step three, ball milling, drying and pre-calcining the second mixture in sequence to obtain main crystal phase powder.

[0011] Step 4: ball milling and drying the main crystalline phase powder in sequence, and then granulating, tableting and sintering in sequence to obtain a lead-free perovskite ceramic material.

[0012] The Bi 0.5 Na 0.5 TiO3 and Ba(Mg 0.5 W 0.5 )O3 has a molar ratio of (1-x):x, where x is 0.01-0.35.

[0013] In a possible implementation, in step 1, the molar ratio of the MgO to the WO3 is (1+a):(1+b), wherein a is 0.01-0.04, and b is 0.01-0.04.

[0014] In a possible implementation, in step 1, the first mixture is sintered at a temperature of 1000-1200° C. and the heat preservation time is 5-10 hours.

[0015] In a possible implementation, in step 2, according to the Bi 0.5 Na 0.5 TiO3 and Ba(Mg 0.5 W 0.5 )O3 is (1-x):x to calculate the molar ratio of Bi2O3, Na2CO3, TiO2, BaCO3 and MgWO4. The reason why the C element disappears is that Bi2O3, Na2CO3, TiO2, BaCO3 and MgWO4 react chemically at high temperature in the subsequent steps to produce CO2 gas.

[0016] In a possible implementation, in step three, the ball milling time is 12 hours, anhydrous ethanol and zirconium oxide balls are added during the ball milling, and the mass ratio of the second mixture, anhydrous ethanol, and zirconium oxide balls is 1:1.5:2.

[0017] In step 3, the drying time is 2-4 hours and the drying temperature is 80-100°C.

[0018] In step three, the pre-burning temperature is 700-900°C, the insulation time is 3-5h, and the heating rate is 3-5°C / min.

[0019] In a possible implementation, in step 4, the ball milling time is 6 hours, anhydrous ethanol and zirconia balls are added during the ball milling, and the mass ratio of the main crystal phase powder, anhydrous ethanol, and zirconia balls is 1:1.5:2.

[0020] In step 4, the drying time is 2-4 hours and the drying temperature is 80-100°C.

[0021] In a possible implementation, in step 4, a binder having a mass concentration of 5%-7% is added to the dried main crystal phase powder for granulation, and 60-mesh and 80-mesh sieves are used to screen out particles between 60 and 80 meshes for tableting.

[0022] The binder is polyvinyl alcohol.

[0023] The pressure during tableting is 6-12MPa.

[0024] In one possible implementation, in step four, when sintering the ceramic green body obtained after tableting, the temperature is first raised to 600°C at a rate of 3°C / min, kept warm for 2-4 hours to remove the binder, then raised to 1100-1250°C at the same rate, kept warm for 3-4 hours, and then cooled to 700°C at a rate of 3°C / min, and naturally cooled to obtain a lead-free perovskite ceramic material.

[0025] In a possible implementation, step 4 also includes: step 5, grinding and cleaning the lead-free perovskite ceramic material, coating silver electrodes on both sides, sintering at 600° C. for 30 minutes, and obtaining a lead-free perovskite ceramic material sample.

[0026] A highly polarized lead-free perovskite ceramic material and preparation method in this application have the following advantages:

[0027] By adding Ba(Mg 0.5 W 0.5 )O3 introduces Bi 0.5 Na 0.5 The lead-free perovskite ceramic material prepared from the TiO3 lead-free relaxor ferroelectric ceramic has a smaller grain size, and the grains are arranged more densely, almost no gaps appear, and the density is good; in addition, the lead-free perovskite ceramic material of the present application is doped with Ba(Mg 0.5 W 0.5 )O3, a large lattice distortion is produced at the B position of the ceramic, and the induced saturation polarization intensity exceeds 90 uC / cm 2 .

[0028] Proposed by Bi0.5 Na 0.5 TiO3 and Ba(Mg 0.5 W 0.5 )O3 solid solution lead-free perovskite ceramic material, the preparation process is simple, the cost is low, suitable for mass production, and the raw materials do not contain lead, is an environmentally friendly ceramic material, in line with the needs of social development.

[0029] A method for preparing a highly polarized lead-free perovskite ceramic material is proposed, wherein MgO and WO3 are first mixed to obtain a first mixture, and the first mixture is sintered to obtain a compound MgWO4, thereby ensuring that Mg 2+ and W 6+ Can enter the B position in a specific proportion, due to Mg 2+ and W 6+ The large difference in ionic radius and electronegativity between them will make the doped Ba(Mg 0.5 W 0.5 )O3 produces a large lattice distortion at the B position, thereby inducing a high saturation polarization intensity. 2+ Doping will increase the hardness of the ceramic, which is beneficial to the improvement of breakdown and ultimately induces a higher saturation polarization intensity. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 A schematic flow chart of a method for preparing a highly polarized lead-free perovskite ceramic material provided in an embodiment of the present application;

[0032] Figure 2 The average grain size and scanning electron microscope image of the lead-free perovskite ceramic material provided in Example 5 of the present application;

[0033] Figure 3 A graph showing the polarization intensity of the lead-free perovskite ceramic material provided in Example 2 of the present application under different electric fields;

[0034] Figure 4 A graph showing the polarization intensity of the lead-free perovskite ceramic material provided in Example 4 of the present application under different electric fields;

[0035] Figure 5 A graph showing the polarization intensity of the lead-free perovskite ceramic material provided in Example 5 of the present application under different electric fields;

[0036] Figure 6 Schematic diagram of the principle of local lattice strain provided in this application. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0038] The present application embodiment provides a highly polarized lead-free perovskite ceramic material comprising Bi 0.5 Na 0.5 TiO3 and Ba(Mg 0.5 W 0.5 )O3 solid solution.

[0039] like Figure 1 As shown, the embodiment of the present application also provides a method for preparing a highly polarized lead-free perovskite ceramic material, comprising the following steps:

[0040] Step 1: Mix MgO and WO3 to obtain a first mixture, and sinter the first mixture to obtain a compound MgWO4.

[0041] Step 2: Mix Bi2O3, Na2CO3, TiO2, BaCO3 and the compound MgWO4 obtained in step 1 to obtain a second mixture.

[0042] Step three, ball milling, drying and pre-calcining the second mixture in sequence to obtain main crystal phase powder.

[0043] Step 4: ball milling and drying the main crystalline phase powder in sequence, and then granulating, tableting and sintering in sequence to obtain a lead-free perovskite ceramic material.

[0044] The Bi 0.5 Na 0.5 TiO3 and Ba(Mg 0.5 W 0.5 )O3 has a molar ratio of (1-x):x, where x is 0.01-0.35.

[0045] Specifically, in step 1, the molar ratio of MgO to WO3 is (1+a):(1+b), where a is 0.01-0.04 and b is 0.01-0.04. The reason for this is that the elements will volatilize at high temperatures, and excessive doping is to ensure that MgO and WO3 can synthesize MgWO4 in a 1:1 ratio.

[0046] Specifically, in step 2, according to the Bi 0.5 Na 0.5 TiO3 and Ba(Mg 0.5 W 0.5 )O3 is (1-x):x to calculate the molar ratio of Bi2O3, Na2CO3, TiO2, BaCO3 and MgWO4. The reason why the C element disappears is that Bi2O3, Na2CO3, TiO2, BaCO3 and MgWO4 react chemically at high temperature in the subsequent steps to produce CO2 gas.

[0047] Specifically, the chemical reaction of Bi2O3, Na2CO3, and TiO2 at high temperature is as follows:

[0048] Bi2O3+Na2CO3+4TiO2 (high temperature) → 4Bi 0.5 Na 0.5 TiO3+CO2.

[0049] The chemical reaction between BaCO3 and MgWO4 at high temperature is as follows:

[0050] 2BaCO3+MgWO4 (high temperature) → 2Ba(Mg 0.5 W 0.5 )O3+2CO2.

[0051] The chemical reactions of Bi2O3, Na2CO3, TiO2, BaCO3 and MgWO4 at high temperatures are as follows:

[0052] (1-x)Bi2O3+(1-x)Na2CO3+4(1-x)TiO2+(4x)BaCO3+(2x)MgWO4(High temperature)→4(Bi 0.5 Na 0.5 ) (1-x) Ba x Ti (1-x) (Mg 0.5 W 0.5 ) x O3+(1+3x)CO2.

[0053] Among them, from the chemical formula of the solid solution (Bi 0.5 Na 0.5 ) (1-x) Ba x Ti (1-x) (Mg 0.5 W 0.5 ) x O3 can see Bi 0.5 Na 0.5 TiO3 and Ba(Mg 0.5W 0.5 )The molar ratio of O3 is (1-x):x.

[0054] Embodiment 1:

[0055] Exemplarily, in step 1, the molar ratio of MgO to WO3 is (1+a):(1+b), wherein a is 0.02 and b is 0.03. The first mixture is sintered at a temperature of 1000° C. for 8 hours.

[0056] Exemplarily, in step 2, according to Bi 0.5 Na 0.5 TiO3 and Ba(Mg 0.5 W 0.5 )O3 is (1-x):x to calculate the molar ratio of Bi2O3, Na2CO3, TiO2, BaCO3 and MgWO4, where the value of x is 0.01.

[0057] Exemplarily, in step 3, the ball milling time is 12 hours, anhydrous ethanol and zirconium oxide balls are added during ball milling, and the mass ratio of the second mixture, anhydrous ethanol, and zirconium oxide balls is 1:1.5:2. The drying time is 4 hours, and the drying temperature is 80°C. The pre-sintering temperature is 850°C, the insulation time is 4 hours, and the heating rate is 4°C / min.

[0058] Exemplarily, in step 4, the ball milling time is 6 hours, anhydrous ethanol and zirconium oxide balls are added during ball milling, and the mass ratio of the main crystalline phase powder, anhydrous ethanol, and zirconium oxide balls is 1:1.5:2. The drying time is 2 hours, and the drying temperature is 100°C. A binder with a mass concentration of 7% is added to the dried main crystalline phase powder for granulation, and 60-mesh and 80-mesh sieves are used to screen out particles between 60 and 80 mesh for tableting. The binder is polyvinyl alcohol. The pressure during tableting is 6MPa.

[0059] Exemplarily, in step four, when sintering the ceramic green body obtained after tableting, the temperature is first raised to 600°C at a rate of 3°C / min, kept warm for 3 hours to remove the binder, then raised to 1150°C at the same rate, kept warm for 3 hours, and then cooled to 700°C at a rate of 3°C / min, and naturally cooled to obtain a lead-free perovskite ceramic material.

[0060] Exemplarily, after step 4, the method further includes: step 5, grinding and cleaning the lead-free perovskite ceramic material, coating silver electrodes on both sides, and sintering at 600° C. for 30 minutes to obtain a lead-free perovskite ceramic material sample.

[0061] Embodiment 2:

[0062] Exemplarily, in step 1, the molar ratio of MgO to WO3 is (1+a):(1+b), wherein a is 0.01 and b is 0.02. The first mixture is sintered at a temperature of 1100° C. for 5 hours.

[0063] Exemplarily, in step 2, according to Bi 0.5 Na 0.5 TiO3 and Ba(Mg 0.5 W 0.5 )O3 is (1-x):x to calculate the molar ratio of Bi2O3, Na2CO3, TiO2, BaCO3 and MgWO4, where the value of x is 0.05.

[0064] Exemplarily, in step 3, the ball milling time is 12 hours, anhydrous ethanol and zirconium oxide balls are added during ball milling, and the mass ratio of the second mixture, anhydrous ethanol, and zirconium oxide balls is 1:1.5:2. The drying time is 3 hours, and the drying temperature is 90°C. The pre-sintering temperature is 700°C, the insulation time is 5 hours, and the heating rate is 3°C / min.

[0065] Exemplarily, in step 4, the ball milling time is 6 hours, anhydrous ethanol and zirconium oxide balls are added during ball milling, and the mass ratio of the main crystalline phase powder, anhydrous ethanol, and zirconium oxide balls is 1:1.5:2. The drying time is 4 hours, and the drying temperature is 80°C. A binder with a mass concentration of 6% is added to the dried main crystalline phase powder for granulation, and 60-mesh and 80-mesh sieves are used to screen out particles between 60 and 80 mesh for tableting. The binder is polyvinyl alcohol. The pressure during tableting is 8MPa.

[0066] Exemplarily, in step four, when the ceramic green body obtained after tableting is sintered, the temperature is first raised to 600°C at a rate of 3°C / min, kept warm for 2 hours to remove the binder, then raised to 1180°C at the same rate, kept warm for 3.5 hours, and then cooled to 700°C at a rate of 3°C / min, and naturally cooled to obtain a lead-free perovskite ceramic material.

[0067] Exemplarily, after step 4, the method further includes: step 5, grinding and cleaning the lead-free perovskite ceramic material, coating silver electrodes on both sides, and sintering at 600° C. for 30 minutes to obtain a lead-free perovskite ceramic material sample.

[0068] Embodiment 3:

[0069] Exemplarily, in step 1, the molar ratio of MgO to WO3 is (1+a):(1+b), wherein a is 0.02 and b is 0.02. The first mixture is sintered at a temperature of 1200° C. for 10 hours.

[0070] Exemplarily, in step 2, according to Bi 0.5 Na 0.5 TiO3 and Ba(Mg 0.5 W 0.5 )O3 is (1-x):x to calculate the molar ratio of Bi2O3, Na2CO3, TiO2, BaCO3 and MgWO4, where the value of x is 0.1.

[0071] Exemplarily, in step 3, the ball milling time is 12 hours, anhydrous ethanol and zirconium oxide balls are added during ball milling, and the mass ratio of the second mixture, anhydrous ethanol, and zirconium oxide balls is 1:1.5:2. The drying time is 2 hours, and the drying temperature is 100°C. The pre-sintering temperature is 900°C, the insulation time is 4 hours, and the heating rate is 5°C / min.

[0072] Exemplarily, in step 4, the ball milling time is 6 hours, anhydrous ethanol and zirconium oxide balls are added during ball milling, and the mass ratio of the main crystalline phase powder, anhydrous ethanol, and zirconium oxide balls is 1:1.5:2. The drying time is 4 hours, and the drying temperature is 80°C. A binder with a mass concentration of 7% is added to the dried main crystalline phase powder for granulation, and 60-mesh and 80-mesh sieves are used to screen out particles between 60 and 80 mesh for tableting. The binder is polyvinyl alcohol. The pressure during tableting is 10MPa.

[0073] Exemplarily, in step four, when the ceramic green body obtained after tableting is sintered, the temperature is first raised to 600°C at a rate of 3°C / min, kept warm for 3 hours to remove the binder, then raised to 1200°C at the same rate, kept warm for 3.5 hours, and then cooled to 700°C at a rate of 3°C / min, and naturally cooled to obtain a lead-free perovskite ceramic material.

[0074] Exemplarily, after step 4, the method further includes: step 5, grinding and cleaning the lead-free perovskite ceramic material, coating silver electrodes on both sides, and sintering at 600° C. for 30 minutes to obtain a lead-free perovskite ceramic material sample.

[0075] Embodiment 4:

[0076] Exemplarily, in step 1, the molar ratio of MgO to WO3 is (1+a):(1+b), wherein a is 0.03 and b is 0.01. The first mixture is sintered at a temperature of 1150° C. for 10 hours.

[0077] Exemplarily, in step 2, according to Bi 0.5 Na 0.5 TiO3 and Ba(Mg 0.5 W 0.5)O3 is (1-x):x to calculate the molar ratio of Bi2O3, Na2CO3, TiO2, BaCO3 and MgWO4, where the value of x is 0.13.

[0078] Exemplarily, in step 3, the ball milling time is 12 hours, anhydrous ethanol and zirconium oxide balls are added during ball milling, and the mass ratio of the second mixture, anhydrous ethanol, and zirconium oxide balls is 1:1.5:2. The drying time is 4 hours, and the drying temperature is 80°C. The pre-sintering temperature is 800°C, the insulation time is 4 hours, and the heating rate is 4°C / min.

[0079] Exemplarily, in step 4, the ball milling time is 6 hours, anhydrous ethanol and zirconium oxide balls are added during ball milling, and the mass ratio of the main crystalline phase powder, anhydrous ethanol, and zirconium oxide balls is 1:1.5:2. The drying time is 3 hours, and the drying temperature is 80°C. A binder with a mass concentration of 5% is added to the dried main crystalline phase powder for granulation, and 60-mesh and 80-mesh sieves are used to screen out particles between 60 and 80 mesh for tableting. The binder is polyvinyl alcohol. The pressure during tableting is 9MPa.

[0080] Exemplarily, in step four, when the ceramic green body obtained after tableting is sintered, the temperature is first raised to 600°C at a rate of 3°C / min, kept warm for 3 hours to remove the binder, then raised to 1160°C at the same rate, kept warm for 3 hours, and then cooled to 700°C at a rate of 3°C / min, and naturally cooled to obtain a lead-free perovskite ceramic material.

[0081] Exemplarily, after step 4, the method further includes: step 5, grinding and cleaning the lead-free perovskite ceramic material, coating silver electrodes on both sides, and sintering at 600° C. for 30 minutes to obtain a lead-free perovskite ceramic material sample.

[0082] Embodiment 5:

[0083] Exemplarily, in step 1, the molar ratio of MgO to WO3 is (1+a):(1+b), wherein a is 0.01 and b is 0.01. The first mixture is sintered at 1150° C. for 7 hours.

[0084] Exemplarily, in step 2, according to Bi 0.5 Na 0.5 TiO3 and Ba(Mg 0.5 W 0.5 )O3 is (1-x):x to calculate the molar ratio of Bi2O3, Na2CO3, TiO2, BaCO3 and MgWO4, where the value of x is 0.18.

[0085] Exemplarily, in step 3, the ball milling time is 12 hours, anhydrous ethanol and zirconium oxide balls are added during ball milling, and the mass ratio of the second mixture, anhydrous ethanol, and zirconium oxide balls is 1:1.5:2. The drying time is 3 hours, and the drying temperature is 85°C. The pre-sintering temperature is 750°C, the insulation time is 3 hours, and the heating rate is 3°C / min.

[0086] Exemplarily, in step 4, the ball milling time is 6 hours, anhydrous ethanol and zirconium oxide balls are added during ball milling, and the mass ratio of the main crystalline phase powder, anhydrous ethanol, and zirconium oxide balls is 1:1.5:2. The drying time is 3 hours, and the drying temperature is 90°C. A binder with a mass concentration of 6% is added to the dried main crystalline phase powder for granulation, and 60-mesh and 80-mesh sieves are used to screen out particles between 60 and 80 mesh for tableting. The binder is polyvinyl alcohol. The pressure during tableting is 12MPa.

[0087] Exemplarily, in step four, when sintering the ceramic green body obtained after tableting, the temperature is first raised to 600°C at a rate of 3°C / min, kept warm for 2 hours to remove the binder, then raised to 1100°C at the same rate, kept warm for 3 hours, and then cooled to 700°C at a rate of 3°C / min, and naturally cooled to obtain a lead-free perovskite ceramic material.

[0088] Exemplarily, after step 4, the method further includes: step 5, grinding and cleaning the lead-free perovskite ceramic material, coating silver electrodes on both sides, and sintering at 600° C. for 30 minutes to obtain a lead-free perovskite ceramic material sample.

[0089] Embodiment 6:

[0090] Exemplarily, in step 1, the molar ratio of MgO to WO3 is (1+a):(1+b), wherein a is 0.03 and b is 0.03. The first mixture is sintered at a temperature of 1050° C. for 10 hours.

[0091] Exemplarily, in step 2, according to Bi 0.5 Na 0.5 TiO3 and Ba(Mg 0.5 W 0.5 )O3 is (1-x):x to calculate the molar ratio of Bi2O3, Na2CO3, TiO2, BaCO3 and MgWO4, where the value of x is 0.21.

[0092] Exemplarily, in step 3, the ball milling time is 12 hours, anhydrous ethanol and zirconium oxide balls are added during ball milling, and the mass ratio of the second mixture, anhydrous ethanol, and zirconium oxide balls is 1:1.5:2. The drying time is 3 hours, and the drying temperature is 100°C. The pre-sintering temperature is 850°C, the insulation time is 4 hours, and the heating rate is 4°C / min.

[0093] Exemplarily, in step 4, the ball milling time is 6 hours, anhydrous ethanol and zirconium oxide balls are added during ball milling, and the mass ratio of the main crystalline phase powder, anhydrous ethanol, and zirconium oxide balls is 1:1.5:2. The drying time is 4 hours, and the drying temperature is 100°C. A binder with a mass concentration of 6% is added to the dried main crystalline phase powder for granulation, and 60-mesh and 80-mesh sieves are used to screen out particles between 60 and 80 mesh for tableting. The binder is polyvinyl alcohol. The pressure during tableting is 10MPa.

[0094] Exemplarily, in step four, when the ceramic green body obtained after tableting is sintered, the temperature is first raised to 600°C at a rate of 3°C / min, kept warm for 4 hours to remove the binder, then raised to 1140°C at the same rate, kept warm for 3 hours, and then cooled to 700°C at a rate of 3°C / min, and naturally cooled to obtain a lead-free perovskite ceramic material.

[0095] Exemplarily, after step 4, the method further includes: step 5, grinding and cleaning the lead-free perovskite ceramic material, coating silver electrodes on both sides, and sintering at 600° C. for 30 minutes to obtain a lead-free perovskite ceramic material sample.

[0096] Embodiment 7:

[0097] Exemplarily, in step 1, the molar ratio of MgO to WO3 is (1+a):(1+b), wherein a is 0.04 and b is 0.01. The first mixture is sintered at a temperature of 1080° C. for 6 hours.

[0098] Exemplarily, in step 2, according to Bi 0.5 Na 0.5 TiO3 and Ba(Mg 0.5 W 0.5 )O3 is (1-x):x to calculate the molar ratio of Bi2O3, Na2CO3, TiO2, BaCO3 and MgWO4, where the value of x is 0.24.

[0099] Exemplarily, in step 3, the ball milling time is 12 hours, anhydrous ethanol and zirconium oxide balls are added during ball milling, and the mass ratio of the second mixture, anhydrous ethanol, and zirconium oxide balls is 1:1.5:2. The drying time is 2 hours, and the drying temperature is 95°C. The pre-sintering temperature is 900°C, the insulation time is 5 hours, and the heating rate is 5°C / min.

[0100] Exemplarily, in step 4, the ball milling time is 6 hours, anhydrous ethanol and zirconium oxide balls are added during ball milling, and the mass ratio of the main crystalline phase powder, anhydrous ethanol, and zirconium oxide balls is 1:1.5:2. The drying time is 4 hours, and the drying temperature is 85°C. A binder with a mass concentration of 5% is added to the dried main crystalline phase powder for granulation, and 60-mesh and 80-mesh sieves are used to screen out particles between 60 and 80 mesh for tableting. The binder is polyvinyl alcohol. The pressure during tableting is 7MPa.

[0101] Exemplarily, in step four, when sintering the ceramic green body obtained after tableting, the temperature is first raised to 600°C at a rate of 3°C / min, kept warm for 2 hours to remove the binder, then raised to 1250°C at the same rate, kept warm for 3 hours, and then cooled to 700°C at a rate of 3°C / min, and naturally cooled to obtain a lead-free perovskite ceramic material.

[0102] Exemplarily, after step 4, the method further includes: step 5, grinding and cleaning the lead-free perovskite ceramic material, coating silver electrodes on both sides, and sintering at 600° C. for 30 minutes to obtain a lead-free perovskite ceramic material sample.

[0103] Embodiment 8:

[0104] Exemplarily, in step 1, the molar ratio of MgO to WO3 is (1+a):(1+b), wherein a is 0.02 and b is 0.01. The first mixture is sintered at a temperature of 1200° C. for 5 hours.

[0105] Exemplarily, in step 2, according to Bi 0.5 Na 0.5 TiO3 and Ba(Mg 0.5 W 0.5 )O3 is (1-x):x to calculate the molar ratio of Bi2O3, Na2CO3, TiO2, BaCO3 and MgWO4, where the value of x is 0.3.

[0106] Exemplarily, in step 3, the ball milling time is 12 hours, anhydrous ethanol and zirconium oxide balls are added during ball milling, and the mass ratio of the second mixture, anhydrous ethanol, and zirconium oxide balls is 1:1.5:2. The drying time is 2 hours, and the drying temperature is 80°C. The pre-sintering temperature is 700°C, the insulation time is 3 hours, and the heating rate is 3°C / min.

[0107] Exemplarily, in step 4, the ball milling time is 6 hours, anhydrous ethanol and zirconium oxide balls are added during ball milling, and the mass ratio of the main crystalline phase powder, anhydrous ethanol, and zirconium oxide balls is 1:1.5:2. The drying time is 4 hours, and the drying temperature is 100°C. A binder with a mass concentration of 6% is added to the dried main crystalline phase powder for granulation, and 60-mesh and 80-mesh sieves are used to screen out particles between 60 and 80 mesh for tableting. The binder is polyvinyl alcohol. The pressure during tableting is 11MPa.

[0108] Exemplarily, in step four, when the ceramic green body obtained after tableting is sintered, the temperature is first raised to 600°C at a rate of 3°C / min, kept warm for 3 hours to remove the binder, then raised to 1230°C at the same rate, kept warm for 4 hours, and then cooled to 700°C at a rate of 3°C / min, and naturally cooled to obtain a lead-free perovskite ceramic material.

[0109] Exemplarily, after step 4, the method further includes: step 5, grinding and cleaning the lead-free perovskite ceramic material, coating silver electrodes on both sides, and sintering at 600° C. for 30 minutes to obtain a lead-free perovskite ceramic material sample.

[0110] Embodiment 9:

[0111] Exemplarily, in step 1, the molar ratio of MgO to WO3 is (1+a):(1+b), wherein a is 0.03 and b is 0.04. The first mixture is sintered at a temperature of 1120° C. for 9 hours.

[0112] Exemplarily, in step 2, according to Bi 0.5 Na 0.5 TiO3 and Ba(Mg 0.5 W 0.5 )O3 is (1-x):x to calculate the molar ratio of Bi2O3, Na2CO3, TiO2, BaCO3 and MgWO4, where the value of x is 0.35.

[0113] Exemplarily, in step 3, the ball milling time is 12 hours, anhydrous ethanol and zirconium oxide balls are added during ball milling, and the mass ratio of the second mixture, anhydrous ethanol, and zirconium oxide balls is 1:1.5:2. The drying time is 4 hours, and the drying temperature is 85°C. The pre-sintering temperature is 800°C, the insulation time is 5 hours, and the heating rate is 4°C / min.

[0114] Exemplarily, in step 4, the ball milling time is 6 hours, anhydrous ethanol and zirconium oxide balls are added during ball milling, and the mass ratio of the main crystalline phase powder, anhydrous ethanol, and zirconium oxide balls is 1:1.5:2. The drying time is 4 hours, and the drying temperature is 100°C. A binder with a mass concentration of 7% is added to the dried main crystalline phase powder for granulation, and 60-mesh and 80-mesh sieves are used to screen out particles between 60 and 80 mesh for tableting. The binder is polyvinyl alcohol. The pressure during tableting is 10MPa.

[0115] Exemplarily, in step four, when the ceramic green body obtained after tableting is sintered, the temperature is first raised to 600°C at a rate of 3°C / min, kept warm for 4 hours to remove the binder, then raised to 1130°C at the same rate, kept warm for 4 hours, and then cooled to 700°C at a rate of 3°C / min, and naturally cooled to obtain a lead-free perovskite ceramic material.

[0116] Exemplarily, after step 4, the method further includes: step 5, grinding and cleaning the lead-free perovskite ceramic material, coating silver electrodes on both sides, and sintering at 600° C. for 30 minutes to obtain a lead-free perovskite ceramic material sample.

[0117] like Figure 2 The figure shows the average grain size and scanning electron microscope image of the lead-free perovskite ceramic material provided in Example 5. Figure 2 It can be seen that the average grain size of the lead-free perovskite ceramic material provided in Example 5 is 0.89 μm, and most of the grains are distributed between 0.4 and 1.2 μm. Figure 2 The scanning electron microscope image also shows that the lead-free perovskite ceramic material provided in Example 5 has a dense microstructure, clear grain boundaries and almost invisible pores, and has good sintering properties, which is conducive to improving breakdown.

[0118] like Figures 3 to 5 The figures show the polarization intensity curves of the lead-free perovskite ceramic materials provided in Examples 2, 4 and 5 of the present application under different electric fields (the polarization value on the vertical axis is the polarization intensity). Figure 3 , Figure 4 , Figure 5 It can be seen that the saturation polarization intensity P of the lead-free perovskite ceramic material provided in Example 2 under an electric field of 260 kV / cm is max Reached 98.68uC / cm 2 , the saturation polarization intensity P of the lead-free perovskite ceramic material provided in Example 4 under an electric field of 220 kV / cm max Reached 96.38uC / cm 2 The saturation polarization intensity P of the lead-free perovskite ceramic material provided in Example 5 under an electric field of 250 kV / cm maxReached 90.43uC / cm 2 In Example 2, Example 4, and Example 5, as the applied electric field increases, the saturation polarization intensity P max are constantly increasing, and the dense microstructure provides the necessary conditions for achieving high saturation polarization.

[0119] Specifically, the lead-free perovskite ceramic material of the present application is prepared by 0.5 Na 0.5 TiO3 doped with Ba(Mg 0.5 W 0.5 )O3, resulting in a large lattice distortion at the B position of the ceramic. The principle of lattice distortion is as follows:

[0120] Principle 1, ionic radius mismatch and local lattice strain:

[0121] Bi 0.5 Na 0.5 The original ion at B position in TiO3 is Ti 4+ (0.605Å)Ba(Mg 0.5 W 0.5 )Mg in O3 2+ (0.72 Å) and W 6+ (0.60 Å) replaces Ti 4+ , whose ion size difference will cause local lattice expansion (Mg 2+ ) or shrinkage (W 6+ ),like Figure 6 This size mismatch causes the oxygen octahedron (TiO6) to distort, forming local lattice strain, which accumulates into macroscopic lattice distortion. 2+ Doped with Bi 0.5 Na 0.5 TiO3, the larger Mg 2+ Occupy Ti position, forcing the surrounding O 2- The ions move outward, causing the octahedron to expand; while W 6+ The smaller size of may cause the octahedron to shrink, and the lattice distortion will be aggravated when the two coexist.

[0122] Principle 2, charge imbalance and defect compensation:

[0123] Ti 4+ Mg 2+ and W 6+ After substitution, the charge imbalance needs to be compensated by defects. According to the following defect equation, oxygen vacancies will be generated after substitution, and the formation of oxygen vacancies will destroy the symmetry of the oxygen octahedron, resulting in long-range lattice distortion:

[0124] .

[0125] Principle 3, bonding characteristics and electronic structure changes:

[0126] Mg 2+ -O bond (strong ionicity) and W 6+ -O bond (strong covalent bond) with the original Ti 4+ The bonding characteristics of the -O bond are different, resulting in changes in bond length and bond angle. 6+ The high electronegativity of Mg may enhance the covalency of the WO bond and shorten the bond length, while 2+ The weak polarizability of Mg may extend the bond length of Mg-O, and the two together aggravate the octahedral distortion.

[0127] In this embodiment of the present application, Ba(Mg 0.5 W 0.5 )O3 introduces Bi 0.5 Na 0.5 The lead-free perovskite ceramic material prepared from the TiO3 lead-free relaxor ferroelectric ceramic has a smaller grain size, and the grains are arranged more densely, almost no gaps appear, and the density is good; in addition, the lead-free perovskite ceramic material of the present application is doped with Ba(Mg 0.5 W 0.5 )O3, a large lattice distortion is produced at the B position of the ceramic, and the induced saturation polarization intensity exceeds 90 uC / cm 2 .

[0128] Proposed by Bi 0.5 Na 0.5 TiO3 and Ba(Mg 0.5 W 0.5 )O3 solid solution lead-free perovskite ceramic material, the preparation process is simple, the cost is low, suitable for mass production, and the raw materials do not contain lead, is an environmentally friendly ceramic material, in line with the needs of social development.

[0129] A method for preparing a highly polarized lead-free perovskite ceramic material is proposed, wherein MgO and WO3 are first mixed to obtain a first mixture, and the first mixture is sintered to obtain a compound MgWO4, thereby ensuring that Mg 2+ and W 6+ Can enter the B position in a specific proportion, due to Mg 2+ and W 6+ The large difference in ionic radius and electronegativity between them will make the doped Ba(Mg 0.5 W 0.5 )O3 produces a large lattice distortion at the B position, thereby inducing a high saturation polarization intensity. 2+ Doping will increase the hardness of the ceramic, which is beneficial to the improvement of breakdown and ultimately induces a higher saturation polarization intensity.

[0130] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0131] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A highly polarized lead-free perovskite ceramic material, characterized in that: By Bi 0.5 Na 0.5 TiO3 and Ba(Mg 0.5 W 0.5 )O3 solid solution, the preparation method comprises the following steps: Step 1, mixing MgO and WO3 to obtain a first mixture, and sintering the first mixture to obtain a compound MgWO4; Step 2, mixing Bi2O3, Na2CO3, TiO2, BaCO3 and the compound MgWO4 obtained in step 1 to obtain a second mixture; Step 3, ball milling, drying and pre-calcining the second mixture in sequence to obtain a main crystal phase powder; Step 4, ball milling and drying the main crystalline phase powder in sequence, and then granulating, tabletting and sintering in sequence to obtain a lead-free perovskite ceramic material; The Bi 0.5 Na 0.5 TiO3 and Ba(Mg 0.5 W 0.5 ) The molar ratio of O3 is (1-x):x, wherein the value of x is 0.01-0.35; In step 1, the molar ratio of the MgO to the WO3 is (1+a):(1+b), wherein the value of a is 0.01-0.04, and the value of b is 0.01-0.04; In step 1, the first mixture is sintered at a temperature of 1000-1200° C. and the heat preservation time is 5-10 hours; In step 3, the pre-burning temperature is 700-900°C, the holding time is 3-5h, and the heating rate is 3-5°C / min; In step 4, when sintering the ceramic green body obtained after tableting, the temperature is first raised to 600°C at a rate of 3°C / min, kept warm for 2-4 hours to remove the binder, then raised to 1100-1250°C at the same rate, kept warm for 3-4 hours, and then cooled to 700°C at a rate of 3°C / min. After natural cooling, a lead-free perovskite ceramic material is obtained.

2. A highly polarized lead-free perovskite ceramic material as claimed in claim 1, characterized in that: In step 3, the ball milling time is 12 hours, anhydrous ethanol and zirconium oxide balls are added during the ball milling, and the mass ratio of the second mixture, anhydrous ethanol, and zirconium oxide balls is 1:1.5:2; In step 3, the drying time is 2-4 hours and the drying temperature is 80-100°C.

3. A highly polarized lead-free perovskite ceramic material as claimed in claim 1, characterized in that: In step 4, the ball milling time is 6 hours, anhydrous ethanol and zirconia balls are added during the ball milling, and the mass ratio of the main crystal phase powder, anhydrous ethanol, and zirconia balls is 1:1.5:2; In step 4, the drying time is 2-4 hours and the drying temperature is 80-100°C.

4. A highly polarized lead-free perovskite ceramic material as claimed in claim 1, characterized in that: In step 4, a binder having a mass concentration of 5% to 7% is added to the dried main crystal phase powder for granulation, and 60-mesh and 80-mesh sieves are used to screen out particles between 60 and 80 meshes for tableting; The binder is polyvinyl alcohol; The pressure during tableting is 6-12MPa.

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