A high-entropy relaxor ferroelectric ceramic material and its preparation method

Abstract

This invention belongs to the field of ceramic materials technology, specifically relating to a high-entropy relaxor ferroelectric ceramic material and its preparation method. The general chemical formula of the high-entropy relaxor ferroelectric ceramic material is (1-x)(Pb). 0.25 Ba 0.25 Sr 0.25 Ca 0.25 TiO3-xNaNbO3, where x is the mole fraction, 0.1≤x≤0.3, the high-entropy relaxor ferroelectric ceramic material of the present invention simultaneously possesses high energy storage density, energy storage efficiency, breakdown field energy and stability.

Description

Technical Field

[0001] This invention belongs to the field of ceramic materials technology, specifically relating to a high-entropy relaxor ferroelectric ceramic material and its preparation method. Background Technology

[0002] Ferroelectric ceramic materials possess excellent dielectric properties such as low dielectric loss and high dielectric constant, making them one of the ideal materials for realizing high energy density ceramic capacitors. They have promising application prospects in pulse power equipment, energy storage devices, and other fields. Relaxor ferroelectric materials among ferroelectric ceramics exhibit superior performance compared to ordinary ferroelectric ceramics, enabling the achievement of higher energy storage efficiency.

[0003] Preparation and Photoelectric Properties of Relaxor Ferroelectric Ceramics, Hou Jie, Master's Thesis, Xi'an University of Technology. This thesis discloses that relaxor ferroelectric ceramic materials are generally prepared using solid-state reaction methods. Common energy storage ceramic material systems include the BT (BaTiO3) system and the BST (Ba 0.5 Sr 0.5 TiO3) system, NN(NaNbO3) system, KNN(K 0.5 Na 0.5 NbO3) system, BNT(Bi 0.5 Na 0.5 The core preparation steps of the TiO3 and AN(AgNbO3) systems include: primary ball milling, primary sieving, pre-calcination, secondary ball milling, secondary sieving, granulation, tableting, debinding, and sintering. The 0.85K TiO3 system is prepared using a solid-state method. 0.5 Na 0.5 NbO3-0.15Bi(Mg 0.5 (Zr 0.95 Hf 0.05 ) 0.5 O3 (0.85 kN-0.15 BMZH) ceramics have a strength of 1.73 J / cm³. 3 recoverable energy storage density (W) rec Furthermore, it exhibits an energy storage efficiency of 83.2% even under a high applied electric field of 250 kV / cm. As the requirements for material performance become increasingly stringent, there is a need to further improve energy storage density, efficiency, and breakdown energy simultaneously. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a high-entropy relaxor ferroelectric ceramic material and its preparation method, wherein the high-entropy relaxor ferroelectric ceramic material simultaneously has high energy storage density, energy storage efficiency, breakdown field energy and stability.

[0005] This invention provides a high-entropy relaxor ferroelectric ceramic material, the general chemical formula of which is (1-x)(Pb). 0.25 Ba 0.25Sr 0.25 Ca 0.25 TiO3-xNaNbO3, where x is the mole fraction, 0.1≤x≤0.3, preferably 0.2-0.3.

[0006] This invention provides a method for preparing the high-entropy relaxor ferroelectric ceramic material, comprising the following steps:

[0007] PbO, BaCO3, SrCO3, CaCO3, TiO2, Na2CO3 and Nb2O5 powders were mixed according to the chemical formula, ball-milled for the first time, dried and sintered at 800~900℃ to obtain calcined powder.

[0008] The calcined powder is ball-milled again, dried, then mixed with a binder, granulated, and compressed into tablets to obtain a sheet material.

[0009] The sheet material is covered with the calcined powder, the binder is removed at 600~650℃, and then sintered at 1200~1250℃ to obtain the high-entropy relaxor ferroelectric ceramic material.

[0010] Preferably, the method for the first and second ball milling is to wet ball mill the powder, anhydrous ethanol and zirconium balls (2-5 mm in diameter) at 200-300 rpm for 12-24 h, wherein the mass ratio of the powder, anhydrous ethanol and zirconium balls is 1:1-1.5:3-4.

[0011] Preferably, the drying temperature is 75~85℃, more preferably 80℃, and the drying time is 10h.

[0012] Preferably, the sintering time at 800~900℃ is 4~6h.

[0013] Preferably, the adhesive is polyvinyl alcohol.

[0014] Preferably, after granulation, the material is sieved (preferably through a 200-mesh sieve) and then pressed into sheet material at 200~250MPa (preferably 225MPa).

[0015] Preferably, the time for removing the adhesive at 600~650℃ is 4~6 hours.

[0016] Preferably, the sintering time at 1200~1250℃ is 3~5h.

[0017] The beneficial effects of this invention are that by controlling the proportion of each element and the value of x, it achieves a high energy storage density with high breakdown electric field resistance and high polarization intensity. Furthermore, by utilizing the polar nanodomain structure of high-entropy relaxor ferroelectric ceramics to enhance the energy storage efficiency of the system, the prepared material achieves a high energy storage density (1.3~2.4 J / cm²).3 It boasts excellent comprehensive performance, including high energy storage efficiency (85~91%), high breakdown field energy, and high stability.

[0018] The present invention enhances the stability of the material's properties. Experiments show that as the entropy (S) of the system increases (x=0.1, S=1.43; x=0.2, S=1.61; x=0.3, S=1.39), the energy storage density and efficiency of the material maintain good stability in the frequency range of 1~120Hz and the temperature range of 40~120℃, and the stability gradually increases. The optimal condition is reached under the maximum entropy component, where the energy storage density and efficiency decrease by only 18.4% and 4.48% in the 1~120Hz range, and by only 8.67% and 4.23% in the 40~120℃ range. Therefore, the high-entropy relaxor ferroelectric ceramic component has an additional effect on enhancing the stability of the material's properties. In addition, the slow element diffusion under high entropy results in a higher degree of grain refinement. Experiments show that the grains are the finest (1.30±0.7μm) under the maximum entropy component of x=0.2, which has an additional effect on enhancing the breakdown field strength. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating the key processes for preparing the high-entropy relaxor ferroelectric ceramic material of this invention.

[0020] Figure 2 The table shows the room temperature PE curves of the ceramic materials in Examples 1-3. Among them, (a) is the bipolar curve of the material with x=0.1, (b) is the bipolar curve of the material with x=0.2, (c) is the bipolar curve of the material with x=0.3, and (d) is the single-stage hysteresis loop of the ceramic materials in Examples 1-3 at room temperature.

[0021] Figure 3 The stability of the ceramic materials in Examples 1-3 is shown in the frequency range of 1-120 Hz. (a), (b), and (c) represent the variable-frequency unipolar hysteresis loops of Examples 1-3, respectively, and (d), (e), and (f) represent the energy storage densities (W) at different frequencies. rec The curves showing the relationship between energy storage efficiency (η) and energy storage efficiency (η).

[0022] Figure 4 The stability of the ceramic materials in Examples 1-3 at 40-120℃ is shown. (a), (b), and (c) represent the variable-temperature unipolar hysteresis loops of Examples 1-3, respectively, and (d), (e), and (f) represent the energy storage densities (W) at different temperatures. rec The curves showing the relationship between energy storage efficiency (η) and energy storage efficiency (η).

[0023] Figure 5 The room temperature PE curve is for the ceramic material in Comparative Example 1.

[0024] Figure 6 The table shows the room temperature energy storage performance of the ceramic material in Comparative Example 2, where (a) is the room temperature PE curve of BNTBT-xNN; and (b) is the energy storage density and energy storage efficiency as the composition changes. Detailed Implementation

[0025] The purpose of this invention is to provide a high-entropy relaxor ferroelectric ceramic material and its preparation method, including a ratio of (Pb) 0.25 Ba 0.25 Sr 0.25 Ca 0.25 The material is prepared by a solid-state synthesis method using TiO3-xNaNbO3, involving composition, wet ball milling, calcination, secondary ball milling, pressing, and sintering to achieve a dense structure. Key process flows are as follows: Figure 1 As shown, the present invention will be further described in detail below with reference to specific examples:

[0026] Example 1

[0027] The object of this invention embodiment is (Pb) 0.25 Ba 0.25 Sr 0.25 Ca 0.25 TiO3-0.2NaNbO3 high-entropy relaxor ferroelectric ceramic material. The preparation method includes the following steps:

[0028] 1. According to the chemical formula (Pb) 0.25 Ba 0.25 Sr 0.25 Ca 0.25 Weigh out PbO, BaCO3, SrCO3, CaCO3, TiO2, Na2CO3 and Nb2O5 powders. In a ball mill jar, mix the powders, anhydrous ethanol and 5mm zirconium balls at a mass ratio of 1:1.2:3.5. The mixture is then ball-milled at 250 rpm for 12 hours. The resulting mixture is dried in an oven at 80℃ for 10 hours and then placed in an alumina crucible. The mixture is then calcined in a muffle furnace at 850℃ for 6 hours to obtain calcined powder.

[0029] 2. The calcined powder is ball-milled twice at 280 rpm for 12 hours and dried. Approximately 0.1 mL of 5 wt% PVA solution is added dropwise for mixing and granulation. After sieving through a 200-mesh sieve, the powder is placed in a 10 mm diameter mold and pressed into discs under a pressure of 225 MPa.

[0030] 3. Place the disc in an alumina crucible and cover it with calcined powder. Transfer the crucible into a muffle furnace, first heat to 650℃ and hold for 4 hours to remove the binder, then heat to 1250℃ and hold for 4 hours for sintering to obtain (Pb). 0.25 Ba 0.25 Sr 0.25 Ca0.25 TiO3-0.2NaNbO3 high-entropy relaxor ferroelectric ceramic materials.

[0031] The specific process steps mentioned above are as follows: Figure 1 As shown.

[0032] Example 2

[0033] The object of this invention embodiment is (Pb) 0.25 Ba 0.25 Sr 0.25 Ca 0.25 TiO3-0.1NaNbO3 high-entropy relaxor ferroelectric ceramic material. According to the chemical formula (Pb... 0.25 Ba 0.25 Sr 0.25 Ca 0.25 Weigh PbO, BaCO3, SrCO3, CaCO3, TiO2, Na2CO3 and Nb2O5 powders into TiO3-0.1NaNbO3, and follow the same steps as in Example 1.

[0034] Example 3

[0035] The object of this invention embodiment is (Pb) 0.25 Ba 0.25 Sr 0.25 Ca 0.25 TiO3-0.3NaNbO3 high-entropy relaxor ferroelectric ceramic material. According to the chemical formula (Pb... 0.25 Ba 0.25 Sr 0.25 Ca 0.25 Weigh PbO, BaCO3, SrCO3, CaCO3, TiO2, Na2CO3 and Nb2O5 powders into TiO3-0.3NaNbO3, and follow the same steps as in Example 1.

[0036] Comparative Example 1

[0037] Comparative Example 1 is Pb without NaNbO3 doping. 0.25 Ba 0.25 Sr 0.25 Ca 0.25 TiO3 was prepared using the same method as in Example 1.

[0038] Comparative Example 2

[0039] The object of this invention embodiment is (1-x)(0.94Bi). 0.5 Na 0.5 TiO3-0.06BaTiO3)-xNaNbO3. The preparation method is the same as in Example 1.

[0040] The breakdown field strength and room temperature energy storage performance of the ceramic materials obtained in Examples 1, 2, and 3 were determined using the polarization-electric field hysteresis loop (PE) method. The results are as follows: Figure 2 As shown, its breakdown field strength under dual-stage PE testing is above 125 kV / cm, while the maximum breakdown field strength under single-stage testing is approximately 160, 180, and 230 kV / cm, respectively. With a NaNbO3 composition of 0.3, its energy storage density and efficiency reach 2.4 J / cm². 3 With a NaNbO3 content of 0.2%, its energy storage density decreased to 1.8 J / cm³, demonstrating excellent energy storage performance. 3 However, the energy storage efficiency increased to 91.6%, while the energy storage density decreased to 1.32 J / cm³ when the NaNbO₃ composition was 0.1%. 3 Its energy storage efficiency remains at 91.4%.

[0041] The energy storage performance stability of the ceramic materials obtained in Examples 1, 2, and 3 under low electric fields in the frequency range of 1–120 Hz and the temperature range of 40–120 °C was determined by variable temperature / frequency PE. The results are as follows: Figure 3 , 4 As shown, it can be observed that its various properties do not fluctuate much with temperature and frequency (standard deviation).

[0042] The room temperature energy storage performance of the material obtained in Comparative Example 1 was determined by the PE method, and the results are as follows: Figure 5 As shown, its breakdown field strength is not high (60 kV / cm), and its energy storage density is relatively low (<1 J / cm). 3 Its energy storage efficiency is low (<80%), and its performance is inferior to that of this embodiment.

[0043] The room temperature energy storage performance of the material obtained in Comparative Example 2 was determined by the PE method, and the results are as follows: Figure 6 As shown, the breakdown field strength of each component is 70 kV / cm, and the energy storage density is approximately 0.1~0.6 J / cm². 3 Its energy storage efficiency is between 5% and 90%, which is inferior to the performance of this embodiment.

[0044] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of protection of this application is limited to these examples; under the concept of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of one or more embodiments of this application as described above, which are not provided in detail for the sake of brevity.

[0045] One or more embodiments in this application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of this application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of one or more embodiments in this application should be included within the protection scope of this application.

Claims

1. A high-entropy relaxor ferroelectric ceramic material, characterized in that, The general chemical formula of the high-entropy relaxor ferroelectric ceramic material is (1-x)(Pb). 0.25 Ba 0.25 Sr 0.25 Ca 0.25 TiO3-xNaNbO3, where x is the mole fraction and x is 0.

3.

2. A method for preparing a high-entropy relaxor ferroelectric ceramic material as described in claim 1, characterized in that, Includes the following steps: PbO, BaCO3, SrCO3, CaCO3, TiO2, Na2CO3 and Nb2O5 powders were mixed according to the chemical formula, ball-milled for the first time, dried and sintered at 800~900℃ to obtain calcined powder. The calcined powder is ball-milled again, dried, then mixed with a binder, granulated, and compressed into tablets to obtain a sheet material. The sheet material is covered with the calcined powder, the binder is removed at 600~650℃, and then sintered at 1200~1250℃ to obtain the high-entropy relaxor ferroelectric ceramic material.

3. The preparation method according to claim 2, characterized in that, The method for the first and second ball milling is to wet ball mill the powder, anhydrous ethanol and zirconium balls at 200-300 rpm, with the mass ratio of powder, anhydrous ethanol and zirconium balls being 1:1-1.5:3-4.

4. The preparation method according to claim 2, characterized in that, The drying temperature is 75~85℃.

5. The preparation method according to claim 2, characterized in that, The sintering time at 800~900℃ is 4~6h.

6. The preparation method according to claim 2, characterized in that, The adhesive is polyvinyl alcohol.

7. The preparation method according to claim 2, characterized in that, After granulation, the material is sieved and then pressed into sheet form at 200-250 MPa.

8. The preparation method according to claim 2, characterized in that, The adhesive removal time is 4 to 6 hours at 600 to 650°C.

9. The preparation method according to claim 2, characterized in that, The sintering time is 3 to 5 hours at 1200 to 1250°C.

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