Lead-free ferroelectric relaxor ceramic material based on local structure strengthening design and preparation method of lead-free ferroelectric relaxor ceramic material

Abstract

The invention discloses a lead-free ferroelectric relaxor ceramic material based on local structure strengthening design and a preparation method thereof, the chemical composition of the ceramic material is BimNanBayTi (1-x) ZrxO3, 0 < = x < = 0.16, 0.45 < = y < = 0.55, and m + n + y = 1. The preferable chemical composition of the material is Bi < 0.25 > Na < 0.25 > Ba < 0.5 > Ti < 1-x > Zr < x > O The material is prepared by adopting a solid-phase sintering process. According to the ceramic, through atomic-scale chemical framework engineering and dynamic relaxation polarization regulation and control, large-radius Ba < 2 + > is introduced to an A site to serve as a lattice expansion framework, ferroelectric activity Bi < 3 + > and small-radius Na < + > cooperatively optimize local polarization displacement, long-range ordered polarization is inhibited by combining the synergistic effect of B site Ti < 4 + > and Zr < 4 + >, and breakthrough performance that the breakdown field strength reaches up to 98 kV / mm, the energy storage density is 24.3 J / cm < 3 > and the efficiency is 92.4% is achieved. The inversion contradiction between the polarization intensity and the breakdown field intensity of the traditional lead-free ceramic is solved, and a novel dielectric material solution with high energy density, low loss and reliability is provided for a high-power pulse power supply and a new energy device.

Description

Technical Field

[0001] The present invention relates to the technical field of dielectric energy storage ceramic materials, and in particular to a lead-free ferroelectric relaxor ceramic material with high energy storage density and efficiency based on a local structure strengthening design, and a preparation method thereof. Background Art

[0002] Lead-free energy storage ceramics are the opposite of lead-containing energy storage ceramics. Traditional energy storage ceramics generally contain lead, such as lead titanate and lead zirconate titanate. Due to the toxicity of lead, the development of lead-free energy storage ceramics has become a key research area for many researchers, focusing on improving energy storage technology and developing high-quality, energy-density dielectric materials. Lead-free energy storage ceramics are primarily nonlinear dielectric materials with ferroelectric and piezoelectric properties. They are insulators that can store energy. When an external electric field is applied, internal charges accumulate on the electrode surface, forming a built-in electric field for energy storage. Lead-free energy storage ceramics are a key material used in dielectric energy storage capacitors. The dielectric capacitor energy storage devices made from lead-free energy storage ceramics are more economical, applicable, safer, and more reliable. They offer outstanding advantages such as ultra-high power density, ultra-fast charge and discharge rates, and no risk of explosion. They have excellent development prospects in the capacitor field and broad application prospects in pulsed power systems, hybrid vehicles, microwave communications, electromagnetic catapults, and other fields.

[0003] Existing lead-free energy storage ceramics generally suffer from an inherent conflict between polarization strength and breakdown field strength: high-polarization materials suffer from low efficiency due to their ferroelectric domain structure, while low-loss designs sacrifice energy storage density. Traditional technologies optimize performance through grain refinement, multiphase composites, or ion doping, but these efforts have been limited. Grain refinement can easily lead to interface defects, resulting in instability in multiphase systems and weakened polarization response due to high entropy. Furthermore, the problem of polarization saturation at high voltage remains unresolved, making it difficult to achieve both high density, high efficiency, and wide temperature-frequency stability. Summary of the Invention

[0004] To address the conflict between energy storage density and efficiency in lead-free relaxor ferroelectric ceramics under high electric fields, the present invention provides a lead-free ferroelectric relaxor ceramic material based on a localized structural enhancement design. This ceramic material has the characteristics of both high energy storage density and high efficiency.

[0005] The present invention provides a lead-free ferroelectric relaxor ceramic material based on the local lattice framework strengthening design and controlling the ratio of different types of ions. The chemical composition is Bi m Na n Ba y Ti 1-x Zr x O3, wherein 0≤x≤0.16, 0.45≤y≤0.55, m+n+y=1. The preferred chemical composition is Bi 0.25 Na 0.25Ba 0.5 Ti 1-x Zr x O3. As x increases within the range of 0≤x≤0.16, the energy storage efficiency first increases and then decreases. Preferably, 0.10≤x≤0.14, and more preferably, x=0.12.

[0006] The present invention controls the ratio of different types of ions and requires the introduction of framework ions (Ba) with a content of about 50% at the A position. 2+ ), about 25% of small radius ions (Na + ), about 25% of ferroelectric active ions (Bi 3+ ), forming a locally extended lattice environment; and adding 4%-16% blocking ions (Zr 4+ ), breaking the polarization order of the B site.

[0007] Through atomic-level chemical framework engineering and dynamic relaxation polarization control, the large radius Ba at the A site 2+ As a lattice extension framework, ferroelectrically active Bi 3+ and small radius Na + Collaborative optimization of local polarization shift; combined with B-site Ti 4+ With Zr 4+ The synergistic effect of the lattice structure (up to 16%) suppresses the long-range ordered polarization, forming a mechanism of local lattice expansion and synergistic enhancement of polarization displacement that allows the polarization displacement to continue to grow with the electric field; achieving a breakdown field strength of up to 98kV / mm and an energy storage density of 24.3J / cm 3 and a breakthrough performance of 92.4% efficiency.

[0008] The present invention also provides a ceramic material Bi m Na n Ba y Ti 1-x Zr x The preparation method of O3 is as follows:

[0009] S1. Mix Bi2O3, Na2CO3, BaCO3, TiO2 and ZrO2 and ball-mill them, then heat them to 820°C for calcination and keep them warm for two hours.

[0010] S2. The calcined powder is ball-milled again, and then a binder is dropped into the ball-milled powder. After the sample is in block form, it is ground into powder, and then poured into a special mold and pressed into a disc.

[0011] S3. Raise the temperature of the wafer to 550°C and keep it at this temperature for two hours to volatilize the binder, then raise the temperature to 1100-1200°C and calcine it at high temperature for two hours to obtain a ceramic wafer.

[0012] S4. Polish the ceramic sheet with sandpaper, plate gold electrodes on both sides of the ceramic sheet using magnetron sputtering, spray gold on each side with 10 mA for 300 seconds, and grind off the gold plated on the side to obtain a lead-free ferroelectric relaxor ceramic material.

[0013] Preferably, in step S1, Bi2O3, Na2CO3, BaCO3, TiO2, and ZrO2 powders are soaked in anhydrous ethanol and ball-milled using a planetary ball mill at a speed of 300-400 rpm for at least 4 hours; the filtered slurry is dried to obtain a powder; and the powder is then calcined. The amount of ethanol used can be freely selected based on the volume of the container used and the uniformity of the grinding, as long as it facilitates uniform grinding and the ethanol evaporates during the subsequent drying process.

[0014] Preferably, in step S2, the ball milling conditions are as follows: the powder obtained after calcining S1 is cooled to room temperature, then soaked in anhydrous ethanol and milled in a planetary ball mill at a speed of 300-400 rpm for at least 16 hours. The filtered slurry is dried to obtain a powder. The binder is a 3%-5% by mass aqueous solution of polyvinyl alcohol. The mass ratio of polyvinyl alcohol to ground powder is 1:5-15. The pressing conditions are as follows: pressing into a 10 mm diameter disc at a pressure of 300 MPa.

[0015] Preferably, in step S3, the optimal temperature conditions for high-temperature calcination are: when 0≤x<0.08, the calcination temperature is selected as 1150° C., and when 0.08≤x≤0.16, the calcination temperature is selected as 1120° C. The heating rate is 5° C. / min.

[0016] Preferably, in step S4, the ceramic sheet is polished to a thickness of 0.3-0.5 mm using sandpaper with a grit size of 400-800 Cw. After being polished to a thickness of 0.2-0.3 mm on the sandpaper, it is easily ground and transferred to a smooth glass surface. Diamond jade powder is mixed with an appropriate amount of clean water and the ceramic sheet is quickly pressed for a moment to polish in an "8" shape to 0.05 mm.

[0017] Preferably, the ion sputtering conditions are: a gold target is selected as the target material, a current of 10 mA is applied when the vacuum is evacuated to less than 3 Pa, and the time is 300 s. This method makes the electrode on the ceramic surface more uniform, thereby stabilizing and improving the breakdown electric field strength.

[0018] Compared with the prior art, the present invention is beneficial in that:

[0019] (1) The present invention provides a sodium bismuth titanate-based relaxor ferroelectric ceramic material (BiTiO2) based on a local lattice framework strengthening design through chemical framework engineering and atomic level design. 0.25 Na 0.25 Ba 0.5 Ti1-x Zr x O3, 0≤x≤0.16). In Bi 0.25 Na 0.25 Ba 0.5 Ti 0.88 Zr 0.12 Achieving a breakthrough in energy storage performance in O3(BNBZT) ceramics: Based on large radius Ba 2+ Construct a local expansion lattice for Bi 3+ / Na + Provides expanded displacement space, coordinated with Zr 4+ Doping suppresses the long-range ordered polarization of the B site, allowing the material to achieve 24.3 J / cm at a field strength of 98 kV / mm. 3 The energy storage density and ultra-high efficiency of 92.4% solve the inverted contradiction between the polarization intensity and breakdown field strength of traditional relaxor ferroelectrics.

[0020] (2) The design strategy of the present invention is universal and can be achieved by replacing framework ions (such as K + ) or ferroelectrically active ions (such as Ag + ) can be expanded to other perovskite systems and fabricated at low cost using conventional solid-phase sintering processes. This provides a new high-performance dielectric material solution for high-power pulse power supplies and new energy devices, combining high energy density, low loss, and reliability.

[0021] Other advantages, objectives and features of the present invention will be reflected in part from the following description and will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the SEM image of the sodium bismuth titanate-based relaxor ferroelectric ceramic prepared in Example 1.

[0023] Figure 2 These are the unipolar hysteresis loop diagrams of sodium bismuth titanate-based ceramic materials with different Zr contents prepared in Examples 1-5.

[0024] Figure 3 3 is a curve showing the change of the unipolar hysteresis loop of the sodium bismuth titanate-based relaxor ferroelectric ceramic prepared in Example 1 with temperature and cycle number.

[0025] Figure 4 The curves showing the change of energy storage density and efficiency of the sodium bismuth titanate-based relaxor ferroelectric ceramics prepared in Example 1 with the electric field. DETAILED DESCRIPTION

[0026] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0027] Example 1

[0028] The method of the present invention is used to prepare sodium bismuth titanate-based ceramic materials with the best energy storage performance. 0.25 Na 0.25 Ba 0.5 Ti 0.88 Zr 0.12 O3:

[0029] (1) According to the chemical dosage ratio, 3.883 g of Bi2O3, 0.8833 g of Na2CO3, 6.578 g of BaCO3, 4.6857 g of TiO2, and 0.9858 g of ZrO2 were weighed and poured into a nylon ball mill, 150-200 ml of anhydrous ethanol was added and ball milled for not less than 4 h. The speed of the planetary ball mill was set to 400 rpm, and the instrument was cooled for 5 min every 15 min. The filtered slurry was placed in a drying furnace and dried for three hours, and the ball-milled powder was poured out. The powder was placed in a crucible and heated to 820°C in a muffle furnace, kept warm for two hours, and cooled to room temperature to obtain a powder.

[0030] (2) The powder calcined in step (1) was soaked in anhydrous ethanol again and ball-milled at 400 r / min using a planetary ball mill for 16-24 hours. The filtered slurry was placed in a drying furnace for three hours and then the powder was poured out.

[0031] (3) The powder from step (2) was poured into a mortar and a polyvinyl alcohol aqueous solution (the polyvinyl alcohol mass concentration in the polyvinyl alcohol aqueous solution was 3%, and the mass ratio of polyvinyl alcohol to powder was 1:10) was dropped into the mortar. After the sample was in a block shape, it was ground into powder, poured into a special mold, and pressed into a 10 mm diameter disc at a pressure of about 300 MPa. The disc was then placed in a muffle furnace and heated to 550°C and kept at this temperature for two hours to remove the binder. The temperature was then raised to 1120°C and kept at this temperature for two hours. All heating processes were carried out at a rate of 5°C / min.

[0032] (4) The sintered ceramic disc was polished to a thickness of 0.3 mm on 400 Cw sandpaper and to 0.2 mm on 800 Cw sandpaper. Finally, gold electrodes were plated on both sides by magnetron sputtering in a chamber with an air pressure of less than 3 Pa. One side was plated with a point electrode. The gold was sprayed on each side with a current of 10 mA for 300 s, and the gold plated on the side was polished off.

[0033] Example 2

[0034] The preparation method of Example 1 is the same as that of Example 1, except that the ceramic material composition is: Bi 0.25 Na 0.25 Ba 0.5 Ti 0.84 Zr 0.16O3, and Bi2O3, Na2CO3, BaCO3, ZrO2 and TiO2 are weighed accordingly according to the chemical dosage ratio.

[0035] Example 3

[0036] The preparation method of Example 1 is the same as that of Example 1, except that the ceramic material composition is: Bi 0.25 Na 0.25 Ba 0.5 Ti 0.92 Zr 0.08 O3, and Bi2O3, Na2CO3, BaCO3, ZrO2 and TiO2 are weighed accordingly according to the chemical dosage ratio.

[0037] Example 4

[0038] The preparation method of Example 1 is the same as that of Example 1, except that the ceramic material composition is: Bi 0.25 Na 0.25 Ba 0.5 Ti 0.96 Zr 0.04 O3, and Bi2O3, Na2CO3, BaCO3, ZrO2, and TiO2 are weighed accordingly according to the chemical dosage ratio.

[0039] Example 5

[0040] The preparation method of Example 1 is the same as that of Example 1, except that the ceramic material composition is: Bi 0.25 Na 0.25 Ba 0.5 TiO3, Bi2O3, Na2CO3, BaCO3 and TiO2 are weighed accordingly according to the chemical dosage ratio.

[0041] Figure 1 This is the grain morphology of the sodium bismuth titanate-based ceramic obtained in Example 1 obtained under a scanning electron microscope. According to statistics, the average grain size of x=0.12 is 1.02 μm.

[0042] Figure 2 The unipolar hysteresis loops of sodium bismuth titanate-based ceramic materials with different Zr contents prepared in Examples 1-5 are shown. In the figure, 0Zr, 4Zr, 8Zr, 12Zr, and 16Zr represent ceramic materials with x being 0, 0.04, 0.08, 0.12, and 0.16, respectively. As can be seen from the figure, the ceramic material prepared in Example 1 has a high resistance to 98 kV mm -1 The unipolar hysteresis loop under the condition of φ is calculated, from which the maximum recoverable energy density of 24.3 J cm -3 , efficiency 92.4%. The sodium bismuth titanate-based ceramics prepared in Example 2 were -1The maximum recoverable energy density can be calculated as 14.6 J / cm 3 The energy storage efficiency reaches 88.7%. The sodium bismuth titanate-based ceramics prepared in Example 3 are -1 The maximum recoverable energy density can be calculated as 16.8 J / cm 3 The energy storage efficiency reaches 86.1%. The sodium bismuth titanate-based ceramics prepared in Example 4 are -1 The maximum recoverable energy density can be calculated as 7.7 J / cm 3 , the energy storage efficiency reaches 85%. The sodium bismuth titanate-based ceramics prepared in Example 5 are -1 The maximum recoverable energy density can be calculated as 5.1 J / cm 3 , the energy storage efficiency reaches 78%. It can be concluded that when the Zr content is 0.12 (x = 0.12), the performance of the prepared ceramic material is the best. When the ceramic material does not contain Zr (x = 0), the performance of the prepared ceramic material is the worst.

[0043] Figure 3 The sodium bismuth titanate-based ceramic prepared in Example 1 is subjected to 50 kV mm -1 From room temperature 20℃ to 120℃ and from 10 1 times to 10 8 The efficiency fluctuation range of the unipolar hysteresis loop under the cycle is within 10%, which shows that its stability is quite excellent.

[0044] Figure 4 The energy storage density and efficiency curves of the sodium bismuth titanate-based relaxor ferroelectric ceramic prepared in Example 1 as a function of electric field are shown. As can be seen from the figure, the energy storage density increases with increasing electric field strength, while the energy storage efficiency remains stable with increasing electric field strength, always above 90%.

[0045] Example 6

[0046] According to the preparation method of Example 1, the difference is that the Ba content is increased and the Bi and Na contents are reduced compared with Example 1. The ceramic material composition is: Bi 0.2 Na 0.2 Ba 0.6 Ti 0.88 Zr 0.12 O3, Bi2O3, Na2CO3, BaCO3, TiO2, ZrO2 were weighed in accordance with the chemical dosage ratio. The lead-free relaxor ferroelectric ceramics prepared in this embodiment were tested at 8kV mm -1 It shows larger hysteresis and lower polarization value.

[0047] Example 7

[0048] According to the preparation method of Example 1, the difference is that the content of Bi and Na is increased and the content of Ba is reduced compared with Example 1. The ceramic material composition is: Bi 0.3 Na 0.3 Ba 0.4 Ti 0.88 Zr 0.12 O3, Bi2O3, Na2CO3, BaCO3, TiO2, ZrO2 were weighed in accordance with the chemical dosage ratio. The lead-free relaxor ferroelectric ceramic prepared in this embodiment was tested at 10 kV mm -1 The bipolar hysteresis loop below begins to bend, indicating that its polarizability has begun to decrease.

[0049] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A lead-free ferroelectric relaxor ceramic material based on local structure strengthening design, characterized in that: By strengthening the design of the local lattice framework and controlling the ratio of different types of ions, a chemical composition of Bi m Na n Ba y Ti 1-x Zr x O3 ceramic material, wherein 0≤x≤0.16, 0.45≤y≤0.55, m+n+y=1.

2. The lead-free ferroelectric relaxor ceramic material based on local structure strengthening design according to claim 1, characterized in that: The chemical composition is Bi 0.25 Na 0.25 Ba 0.5 Ti 1-x Zr x O3.

3. The lead-free ferroelectric relaxor ceramic material based on local structure strengthening design according to claim 2, characterized in that: x＝0.12。 4. A method for preparing a lead-free ferroelectric relaxor ceramic material based on local structure strengthening design according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1. Mix Bi2O3, Na2CO3, BaCO3, TiO2 and ZrO2 and ball-mill them, then heat them to 820℃ for calcination and keep them at this temperature for two hours. S2, the calcined powder is ball-milled again, and then a binder is dripped into the ball-milled powder. After the sample is in a block shape, it is ground into powder, and then poured into a special mold and pressed into a disc; S3, heating the wafer to 550°C and keeping the temperature for two hours to volatilize the binder, then heating it to 1100-1200°C and calcining it at high temperature for two hours to obtain a ceramic wafer; S4. Polish the ceramic sheet with sandpaper, plate gold electrodes on both sides of the ceramic sheet using magnetron sputtering, spray gold on each side with 10 mA for 300 seconds, and grind off the gold plated on the side to obtain a lead-free ferroelectric relaxor ceramic material.

5. The method for preparing a lead-free ferroelectric relaxor ceramic material based on a local structure strengthening design according to claim 4, wherein: In step S1, Bi2O3, Na2CO3, BaCO3, TiO2 and ZrO2 powders are soaked in anhydrous ethanol and ball-milled using a planetary ball mill. The filtered slurry is dried to obtain powder, and then the powder is calcined.

6. The method for preparing a lead-free ferroelectric relaxor ceramic material based on local structure strengthening design according to claim 4, characterized in that: In step S2, the binder is a polyvinyl alcohol aqueous solution with a mass fraction of 3%-5%.

7. The method for preparing a lead-free ferroelectric relaxor ceramic material based on a local structure strengthening design according to claim 6, wherein: In step S2, the pressing condition is: pressing into a disc with a diameter of 10 mm at a pressure of 300 MPa.

8. The method for preparing a lead-free ferroelectric relaxor ceramic material based on local structure strengthening design according to claim 4, characterized in that: In step S3, the optimal temperature condition for high-temperature calcination is: when 0≤x<0.08, the calcination temperature is selected as 1150°C; when 0.08≤x≤0.16, the calcination temperature is selected as 1120°C.

9. The method for preparing a lead-free ferroelectric relaxor ceramic material based on local structure strengthening design according to claim 4, characterized in that: In step S3, the heating rate is 5°C / min.

10. The method for preparing a lead-free ferroelectric relaxor ceramic material based on local structure strengthening design according to claim 4, characterized in that: In step S4, the ceramic sheet is polished using sandpaper to a thickness of 0.3-0.5 mm.

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