Lead-free high-entropy relaxor ferroelectric material and preparation method thereof

Abstract

The invention belongs to the technical field of functional ceramic materials, and provides a lead-free high-entropy relaxor ferroelectric material and a preparation method thereof.The raw materials of the lead-free high-entropy relaxor ferroelectric material comprise ceramic powder and oxide; the chemical general formula of the ceramic powder is (1-x) (Bi < 0.2 > Na < 0.2 > Ba < 0.2 > Sr < 0.2 > Ca < 0.2 >) TiO < 3-x > La (Mg < 1 / 2 > Zr < 1 / 2 >) O3. The ceramic powder is prepared through a high-entropy strategy, a slender ferroelectric hysteresis loop is obtained at the room temperature, the breakdown field strength of the material is obviously improved, meanwhile, high energy storage density and energy storage efficiency are obtained, the energy storage density reaches 13.5 J cm <-3 >, the energy storage efficiency is 94.6%, and the breakdown electric field reaches up to 750 kV cm <-1 >. According to the material design based on the high-entropy strategy, the relaxation characteristic of the material is remarkably improved, the dielectric loss of the ceramic is effectively reduced, and the practical application potential is shown.

Description

Technical Field

[0001] This invention relates to the field of functional ceramic materials technology, and in particular to a lead-free high-entropy relaxor ferroelectric material and its preparation method. Background Technology

[0002] With the continuous advancement of modern technology, electronic information products, while providing convenience for daily life, also face higher performance requirements. The miniaturization, lightweighting, and smart wearable technologies of electronic products have become future trends, and energy issues have gradually become a focus of social concern. Against this backdrop, developing green and clean new energy sources and materials, while optimizing related processes to improve their performance, has become a key area of ​​current research. Furthermore, the search for new energy storage materials that can replace traditional energy materials is particularly urgent.

[0003] Recent studies have shown that high-entropy strategies, as an effective and flexible method, can significantly improve the physical properties of ferroelectrics by finely controlling local polarization configurations and introducing entropy-related intrinsic effects. High-entropy strategies typically introduce thermodynamic high-entropy effects, crystallographic lattice distortion effects, kinetic hysteresis diffusion effects, and cocktail effects, making them a novel approach to improving the energy storage behavior of dielectric materials. Chen et al., publishing in *Nat. Commun.*, induced local polymorphic distortions by introducing multiple elements at the A-site and B-site of the perovskite structure to control entropy, including multiphase nanoclusters and random tilting of oxygen octahedra. This enhanced the breakdown electric field and delayed polarization saturation, significantly improving the energy storage performance of KNN-based ceramics, achieving a value of 10.06 J / cm². -3 High energy storage density and 90.8% energy storage efficiency. Wu et al. published in Chem. Eng. J. on the high energy storage density and 90.8% energy storage efficiency of Na. 0.5 Bi 0.5 ) 0.75 Sr 0.25 TiO3 is used for entropy regulation to introduce Al into the B site. 3+ Zr 4+ Hf 4+ 、Nb 5+ Plasma, making (Na 0.5 Bi 0.5 ) 0.75 Sr 0.25 Ti 1-x (Al 1 / 4 Zr 1 / 4 Hf 1 / 4 Nb 1 / 4 ) x O3 ceramics have achieved improved energy storage performance, with energy storage density and efficiency at 400 kV / cm². -1 Under moderate electric fields, it can reach 7.4 J / cm². -3And 82.3%. However, existing lead-free high-entropy relaxor ferroelectric ceramics still cannot achieve a balance between high energy density and efficiency under high electric fields, and it is necessary to prepare relaxor ferroelectric materials that have both high energy density and efficiency. Summary of the Invention

[0004] The purpose of this invention is to address the problem of insufficient optimization of the energy storage performance of existing ceramic materials by providing a lead-free high-entropy relaxor ferroelectric material and its preparation method.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a lead-free high-entropy relaxor ferroelectric material, wherein the raw materials of the lead-free high-entropy relaxor ferroelectric material comprise ceramic powder and oxides; the general chemical formula of the ceramic powder is: (1-x)(Bi 0.2 Na 0.2 Ba 0.2 Sr 0.2 Ca 0.2 TiO3-xLa(Mg) 1 / 2 Zr 1 / 2 O3;

[0007] Where x ranges from 0 to 0.2.

[0008] Preferably, the oxide comprises MnO2, ZnO, Li2CO3 and Sm2O3;

[0009] The mass of MnO2 is 0.3% to 0.7% of the mass of the ceramic powder raw material;

[0010] The mass of ZnO is 0.05 to 0.2% of the mass of the ceramic powder raw material;

[0011] The mass of Li2CO3 is 0.1% to 0.3% of the mass of the ceramic powder raw material;

[0012] The mass of Sm2O3 is 0.1 to 0.22% of the mass of the ceramic powder raw material.

[0013] Preferably, the configurational entropy ΔS of the lead-free high-entropy relaxor ferroelectric material config ≥1.61R.

[0014] The present invention also provides a method for preparing the lead-free high-entropy relaxor ferroelectric material, comprising the following steps:

[0015] (1) Weigh the ceramic powder raw materials, mix them, and then pre-fire them to obtain ceramic powder;

[0016] (2) The ceramic powder and oxide are mixed to obtain the casting slurry powder;

[0017] (3) The cast slurry powder, solvent, dispersant, binder, plasticizer and homogenizer are mixed and then pressed, debinded and sintered in sequence to obtain the lead-free high entropy relaxation ferroelectric material.

[0018] Preferably, the ceramic powder raw materials in step (1) are Bi2O3, Na2CO3, BaCO3, SrCO3, CaCO3, La2O3, MgO, ZrO2 and TiO2;

[0019] In step (1), the ball milling speed is 400-500 rpm and the ball milling time is 12-18 h;

[0020] The target temperature for preheating in step (1) is 880-950℃, the target temperature for cooling is 800-870℃, the cooling rate is 5-10℃ / min, and the holding time after reaching the target temperature is 3-4h.

[0021] Preferably, the ball milling speed in step (2) is 500-650 rpm and the ball milling time is 10-12 h; the particle size of the cast slurry powder in step (2) is 150-250 mesh.

[0022] Preferably, the solvent in step (3) comprises ethanol and butanone; the mass of ethanol is 20-30% of the mass of the cast slurry powder; the mass of butanone is 40-50% of the mass of the cast slurry powder.

[0023] The dispersant mentioned in step (3) is one or more of castor oil, fish oil, phosphate esters and tributyl phosphate;

[0024] The mass of the dispersant is 2-5% of the mass of the cast slurry powder.

[0025] Preferably, the adhesive in step (3) is one or more of polyvinyl butyral, polyvinyl alcohol and methylcellulose;

[0026] The mass of the binder is 8-10% of the mass of the cast slurry powder;

[0027] The plasticizer mentioned in step (3) is one or more of polyethylene glycol, triethyl citrate, dibutyl sebacate and dibutyl phthalate;

[0028] The mass of the plasticizer is 2.5% to 8% of the mass of the cast slurry powder;

[0029] The homogenizer mentioned in step (3) is cyclohexanone;

[0030] The mass of the homogenizer is 0.5 to 1.1% of the mass of the cast slurry powder.

[0031] Preferably, the pressing pressure in step (3) is 150-200 MPa, and the holding time is 10-15 min;

[0032] The temperature for discharging adhesive in step (3) is 500-650℃, the heating rate is 0.3-1℃ / min, and the holding time is 4-7h.

[0033] Preferably, the sintering temperature in step (3) is 1180-1240℃, the heating rate is 1-5℃ / min, and the holding time is 2-4h.

[0034] This invention provides a lead-free high-entropy relaxor ferroelectric material, wherein the raw materials of the lead-free high-entropy relaxor ferroelectric material comprise ceramic powder and oxides; the general chemical formula of the ceramic powder is: (1-x)(Bi 0.2 Na 0.2 Ba 0.2 Sr 0.2 Ca 0.2 TiO3-xLa(Mg) 1 / 2 Zr 1 / 2 O3. This invention prepares ceramic powder using a high-entropy strategy, resulting in a fine hysteresis loop at room temperature. This significantly improves the material's breakdown field strength and simultaneously achieves high energy storage density and efficiency, with an energy storage density reaching 13.5 J / cm³. -3 The energy storage efficiency is 94.6%, and the breakdown electric field is as high as 750kV cm. -1 This material design based on a high-entropy strategy significantly improves the relaxation characteristics of the material, effectively reduces the dielectric loss of the ceramic, and significantly enhances energy storage performance and breakdown electric field strength, thus strongly promoting the application and development of ferroelectric materials in the field of energy storage. Furthermore, the overall performance of this material is comparable to current commercial lead-based ceramic capacitor materials, demonstrating its potential for practical applications.

[0035] The lead-free relaxor ceramic material provided by this invention employs a two-step pre-firing method during preparation, which improves the density of the ceramic material to a certain extent and makes its hysteresis loop more slender, thereby obtaining better energy storage performance.

[0036] This invention enhances the stability of ceramic components by adding oxides, and the material preparation is lead-free, environmentally friendly, and the preparation process is simple, highly operable, and has a low overall cost. Attached Figure Description

[0037] Figure 1 X-ray diffraction patterns of the lead-free high-entropy relaxor ferroelectric materials prepared in Examples 1-4;

[0038] Figure 2 SEM image of the lead-free high-entropy relaxor ferroelectric material prepared in Example 1;

[0039] Figure 3 The dielectric temperature spectra of the lead-free high-entropy relaxor ferroelectric materials prepared in Examples 1-4 are shown.

[0040] Figure 4 This is a comparison diagram of the hysteresis loops of the lead-free high-entropy relaxor ferroelectric materials prepared in Examples 1-2 and Comparative Examples 1-2, measured at room temperature.

[0041] Figure 5 The graph shows the energy storage density and energy storage efficiency of the lead-free high-entropy relaxor ferroelectric material prepared in Example 1 under different electric fields. Detailed Implementation

[0042] This invention provides a lead-free high-entropy relaxor ferroelectric material, wherein the raw materials of the lead-free high-entropy relaxor ferroelectric material comprise ceramic powder and oxides; the general chemical formula of the ceramic powder is: (1-x)(Bi 0.2 Na 0.2 Ba 0.2 Sr 0.2 Ca 0.2 TiO3-xLa(Mg) 1 / 2 Zr 1 / 2 O3;

[0043] Where x ranges from 0 to 0.2.

[0044] In this invention, x is preferably 0.05 to 0.19, more preferably 0.06 to 0.18, and even more preferably 0.1 to 0.15.

[0045] In this invention, the oxide comprises MnO2, ZnO, Li2CO3 and Sm2O3.

[0046] In this invention, the mass of MnO2 is preferably 0.3 to 0.7% of the mass of the ceramic powder raw material, more preferably 0.4 to 0.6%, and even more preferably 0.45 to 0.55%.

[0047] In this invention, the mass of ZnO is preferably 0.05-0.2% of the mass of the ceramic powder raw material, more preferably 0.1-0.15%, and even more preferably 0.12-0.13%.

[0048] In this invention, the mass of Li2CO3 is preferably 0.1 to 0.3% of the mass of the ceramic powder raw material, more preferably 0.15 to 0.25%, and even more preferably 0.18 to 0.22%.

[0049] In this invention, the mass of Sm2O3 is preferably 0.1-0.22% of the mass of the ceramic powder raw material, more preferably 0.15-0.2%, and even more preferably 0.16-0.18%.

[0050] In this invention, the configurational entropy ΔS of the lead-free high-entropy relaxor ferroelectric material config Preferably ≥1.61R, further preferably ≥1.96R, and even more preferably ≥2.31R.

[0051] The present invention also provides a method for preparing the lead-free high-entropy relaxor ferroelectric material, comprising the following steps:

[0052] (1) Weigh the ceramic powder raw materials, mix them, and then pre-fire them to obtain ceramic powder;

[0053] (2) The ceramic powder and oxide are mixed to obtain the casting slurry powder;

[0054] (3) The cast slurry powder, solvent, dispersant, binder, plasticizer and homogenizer are mixed and then pressed, debinded and sintered in sequence to obtain the lead-free high entropy relaxor ferroelectric material.

[0055] In this invention, the ceramic powder raw materials mentioned in step (1) are Bi2O3, Na2CO3, BaCO3, SrCO3, CaCO3, La2O3, MgO, ZrO2 and TiO2.

[0056] In this invention, in step (1), zirconium oxide balls and anhydrous ethanol are used as the medium for ball milling.

[0057] In this invention, the ball milling speed in step (1) is preferably 400-500 rpm, more preferably 420-480 rpm, and even more preferably 440-460 rpm; the ball milling time is preferably 12-18 h, more preferably 13-17 h, and even more preferably 14-16 h.

[0058] In this invention, the target temperature for preheating in step (1) is preferably 880-950°C, more preferably 890-940°C, and even more preferably 900-930°C; the target temperature for cooling is preferably 800-870°C, more preferably 810-860°C, and even more preferably 820-850°C; after reaching the target temperature for heating, cooling is started to reduce the temperature to the target temperature for cooling; the cooling rate is preferably 5-10°C / min, more preferably 6-9°C / min, and even more preferably 7-8°C / min; the holding time after reaching the target temperature for cooling is preferably 3-4h, more preferably 3.2-3.8h, and even more preferably 3.4-3.6h.

[0059] In this invention, step (2) involves ball milling using zirconia balls and anhydrous ethanol as the medium.

[0060] In this invention, the ball milling speed for mixing in step (2) is preferably 500-650 rpm, more preferably 550-600 rpm, and even more preferably 560-580 rpm; the ball milling time is preferably 10-12 h, more preferably 10.5-11.5 h, and even more preferably 10.8-11.2 h; and drying is performed after mixing.

[0061] In this invention, the particle size of the cast slurry powder in step (2) is preferably 150-250 mesh, more preferably 160-240 mesh, and even more preferably 180-220 mesh.

[0062] In this invention, the solvent in step (3) comprises ethanol and butanone; the mass of ethanol is preferably 20-30% of the mass of the casting slurry powder, more preferably 22-28%, and more preferably 24-26%; the mass of butanone is preferably 40-50% of the mass of the casting slurry powder, more preferably 42-48%, and more preferably 44-46%.

[0063] In this invention, the dispersant in step (3) is one or more of castor oil, fish oil, phosphate ester and tributyl phosphate.

[0064] In this invention, the mass of the dispersant is preferably 2 to 5% of the mass of the cast slurry powder, more preferably 2.5 to 4.5%, and even more preferably 3 to 4%.

[0065] In this invention, the adhesive in step (3) is one or more of polyvinyl butyral, polyvinyl alcohol and methylcellulose.

[0066] In this invention, the mass of the binder is preferably 8-10% of the mass of the cast slurry powder, more preferably 8.5-9.5%, and even more preferably 8.8-9.2%.

[0067] In this invention, the plasticizer mentioned in step (3) is one or more of polyethylene glycol, triethyl citrate, dibutyl sebacate and dibutyl phthalate.

[0068] In this invention, the mass of the plasticizer is preferably 2.5 to 8% of the mass of the cast slurry powder, more preferably 3 to 7%, and even more preferably 4 to 6%.

[0069] In this invention, the homogenizer in step (3) is cyclohexanone.

[0070] In this invention, the mass of the homogenizer is preferably 0.5 to 1.1% of the mass of the cast slurry powder, more preferably 0.6 to 1%, and even more preferably 0.7 to 0.8%.

[0071] In this invention, the pressing pressure in step (3) is preferably 150-200 MPa, more preferably 160-190 MPa, and even more preferably 170-180 MPa; the holding time is preferably 10-15 min, more preferably 11-14 min, and even more preferably 12-13 min.

[0072] In this invention, a ceramic green body is obtained after pressing, and then the ceramic green body is subjected to subsequent processing.

[0073] In this invention, the temperature of the adhesive discharge in step (3) is preferably 500-650℃, more preferably 550-600℃, and even more preferably 560-580℃; the heating rate is preferably 0.3-1℃ / min, more preferably 0.4-0.8℃ / min, and even more preferably 0.5-0.7℃ / min; the heat preservation time is preferably 4-7h, more preferably 5-6h, and even more preferably 5.4-5.6h.

[0074] In this invention, the sintering temperature in step (3) is preferably 1180-1240℃, more preferably 1190-1230℃, and even more preferably 1200-1220℃; the heating rate is preferably 1-5℃ / min, more preferably 2-4℃ / min, and even more preferably 2.5-3℃ / min; the holding time is preferably 2-4h, more preferably 2.5-3.5h, and even more preferably 2.6-3.4h.

[0075] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0076] Example 1

[0077] Based on stoichiometry for 0.85 (Bi) 0.2 Na 0.2 Ba 0.2 Sr 0.2 Ca 0.2 TiO3-0.15La(Mg) 1 / 2 Zr 1 / 2Raw materials for O3 ceramics were weighed as follows: 12.4357g Bi2O3, 2.8060g Na2CO3, 10.0318g BaCO3, 7.5048g SrCO3, 5.0881g CaCO3, 7.2347g La2O3, 20.3009g TiO2, 0.8957g MgO, and 2.7635g ZrO2 were weighed separately and placed in a nylon jar. The powder was then ball-milled at 450 rpm for 15 hours using zirconia balls and anhydrous ethanol as the milling medium. The powder was then placed in a crucible and heated to 900℃, then cooled to 850℃ at a rate of 10℃ / min and held at that temperature for 3 hours to obtain ceramic powder.

[0078] Weigh 0.3g of MnO2, 0.048g of ZnO, 0.12g of Li2CO3 and 0.13g of Sm2O3, and ball mill them with ceramic powder at 600rpm for 12 hours. After drying, pass the mixture through a 200-mesh sieve to obtain cast slurry powder.

[0079] 50g of casting slurry powder was mixed with 21g of butanone, 11g of anhydrous ethanol, 1g of tributyl phosphate, 0.5g of fish oil, 4.25g of polyvinyl butyral, 1.5g of polyethylene glycol, 1.5g of dibutyl phthalate, and 0.5g of cyclohexanone to obtain a stable casting slurry. The slurry was then cast, cut, and pressed at 180MPa for 15min to obtain a ceramic green body. The green body was placed in a muffle furnace and heated to 550℃ at a rate of 0.5℃ / min, held for 5 hours for debinding, and then heated to 1220℃ at a rate of 3℃ / min and held for 3 hours to obtain a lead-free high-entropy relaxor ferroelectric material with a configurational entropy ΔS. config It is 2.32R.

[0080] Example 2

[0081] Based on stoichiometry for 0.8 (Bi) 0.2 Na 0.2 Ba 0.2 Sr 0.2 Ca 0.2 TiO3-0.2La(Mg) 1 / 2 Zr 1 / 2Raw materials for O3 ceramics were weighed as follows: 11.5633g Bi2O3, 2.6091g Na2CO3, 9.3280g BaCO3, 6.9783g SrCO3, 4.7311g CaCO3, 9.5301g La2O3, 18.8767g TiO2, 1.1798g MgO, and 3.6403g ZrO2 were weighed separately and placed in a nylon jar. The powder was then ball-milled at 420 rpm for 14 hours using zirconia balls and anhydrous ethanol as the milling medium. The powder was then placed in a crucible and heated to 880℃, then cooled to 830℃ at a rate of 10℃ / min and held at that temperature for 3 hours to obtain ceramic powder.

[0082] Weigh 0.33g of MnO2, 0.06g of ZnO, 0.14g of Li2CO3 and 0.129g of Sm2O3, and ball mill them with ceramic powder at 600rpm for 12 hours. After drying, pass the mixture through a 200-mesh sieve to obtain cast slurry powder.

[0083] 50g of casting slurry powder was mixed with 20g of butanone, 10g of anhydrous ethanol, 1g of phosphate ester, 4g of polyvinyl butyral, 1.75g ​​of polyethylene glycol, 1.75g ​​of dibutyl phthalate, and 0.45g of cyclohexanone to obtain a stable casting slurry. The slurry was then cast, cut, and pressed at 190MPa for 12min to obtain a ceramic green body. The green body was placed in a muffle furnace and heated to 550℃ at a rate of 0.6℃ / min, held for 5 hours for debinding, and then heated to 1200℃ at a rate of 3℃ / min and held for 3 hours to obtain a lead-free high-entropy relaxor ferroelectric material with a configurational entropy ΔS. config It is 2.43R.

[0084] Example 3

[0085] Based on stoichiometry for 0.9 (Bi) 0.2 Na 0.2 Ba 0.2 Sr 0.2 Ca 0.2 TiO3-0.1La(Mg) 1 / 2 Zr 1 / 2Raw materials for O3 ceramics were weighed as follows: 13.3296g Bi2O3, 3.0077g Na2CO3, 10.7529g BaCO3, 8.0443g SrCO3, 5.4538g CaCO3, 4.8826g La2O3, 21.7603g TiO2, 0.6045g MgO, and 1.8650g ZrO2 were weighed separately and placed in a nylon jar. The powder was then ball-milled at 480 rpm for 17 hours using zirconia balls and anhydrous ethanol as the milling medium. The powder was then placed in a crucible and heated to 890℃, then cooled to 840℃ at a rate of 10℃ / min and held at that temperature for 3 hours to obtain ceramic powder.

[0086] Weigh 0.27g of MnO2, 0.04g of ZnO, 0.09g of Li2CO3 and 0.12g of Sm2O3, and ball mill them with ceramic powder at 600rpm for 12 hours. After drying, pass the mixture through a 200-mesh sieve to obtain cast slurry powder.

[0087] 50g of casting slurry powder was mixed with 22g of butanone, 12g of anhydrous ethanol, 1.5g of tributyl phosphate, 4g of polyvinyl butyral, 0.5g of polyvinyl alcohol, 1.5g of polyethylene glycol, 1.5g of triethyl citrate, and 0.45g of cyclohexanone to obtain a stable casting slurry. The slurry was then cast, cut, and pressed at 200MPa for 11min to obtain a ceramic green body. The green body was placed in a muffle furnace and heated to 550℃ at a rate of 1℃ / min, held for 5 hours for debinding, and then heated to 1190℃ at a rate of 3℃ / min and held for 3 hours to obtain a lead-free high-entropy relaxor ferroelectric material with a configurational entropy ΔS. config It is 2.17R.

[0088] Example 4

[0089] Based on stoichiometry for 0.95 (Bi) 0.2 Na 0.2 Ba 0.2 Sr 0.2 Ca 0.2 TiO3-0.05La(Mg) 1 / 2 Zr 1 / 2Raw materials for O3 ceramics were weighed as follows: 14.2459g Bi2O3, 3.2144g Na2CO3, 11.4921g BaCO3, 8.5972g SrCO3, 5.8287g CaCO3, 2.4718g La2O3, 23.2561g TiO2, 0.3060g MgO, and 0.9442g ZrO2 were weighed separately and placed in a nylon jar. The powder was then ball-milled at 480 rpm for 17 hours using zirconia balls and anhydrous ethanol as the milling medium. The powder was then placed in a crucible and heated to 920℃, then cooled to 870℃ at a rate of 10℃ / min and held at that temperature for 3 hours to obtain ceramic powder.

[0090] Weigh 0.38g of MnO2, 0.11g of ZnO, 0.15g of Li2CO3 and 0.124g of Sm2O3, and ball mill them with ceramic powder at 600rpm for 12 hours. After drying, pass the mixture through a 200-mesh sieve to obtain cast slurry powder.

[0091] 50g of casting slurry powder was mixed with 23g of butanone, 13g of anhydrous ethanol, 1.75g ​​of castor oil, 4.75g of methylcellulose, 1.25g of polyethylene glycol, 1.25g of dibutyl sebate, and 0.48g of cyclohexanone to obtain a stable casting slurry. The slurry was then cast, cut, and pressed at 150MPa for 15min to obtain a ceramic green body. The green body was placed in a muffle furnace and heated to 550℃ at a rate of 1℃ / min, held for 5 hours for debinding, and then heated to 1230℃ at a rate of 3℃ / min and held for 3 hours to obtain a lead-free high-entropy relaxor ferroelectric material with a configurational entropy ΔS. config It is 1.96R.

[0092] Comparative Example 1

[0093] The difference between Comparative Example 1 and Example 1 is that no oxides were added and no high-energy ball milling was performed. The obtained ceramic powder was directly mixed with 21g of butanone, 11g of anhydrous ethanol, 1g of tributyl phosphate, 0.5g of fish oil, 4.25g of polyvinyl butyral, 1.5g of polyethylene glycol, 1.5g of dibutyl phthalate and 0.5g of cyclohexanone to obtain a stable casting slurry, and then the same subsequent processing as in Example 1 was performed.

[0094] Comparative Example 2

[0095] The difference between Comparative Example 2 and Example 2 is that no oxides are added. The obtained ceramic powder is subjected to high-energy ball milling, drying and sieving to obtain cast slurry powder, and then subjected to the same subsequent processing as in Example 2.

[0096] Performance testing

[0097] The XRD patterns of the lead-free high-entropy relaxor ferroelectric materials prepared in Examples 1-4 are shown below. Figure 1 As shown in the spectrum, the samples of Examples 1-4 have a pure perovskite structure with no second phase, indicating that with the development of La(Mg) 1 / 2 Zr 1 / 2 The introduction of O3 did not significantly affect the sample structure. The shift of the X-ray diffraction peaks to lower angles indicates lattice expansion.

[0098] SEM image of the lead-free high-entropy relaxor ferroelectric material prepared in Example 1 is shown below. Figure 2 As shown, the SEM images reveal that the sample with x = 0.15, i.e., Example 1, has a dense microstructure.

[0099] The dielectric temperature spectra of the lead-free high-entropy relaxor ferroelectric materials prepared in Examples 1-4 are shown below. Figure 3 As shown in the figure, it can be seen that with the increase of La(Mg) 1 / 2 Zr 1 / 2 With increased O3 content, the dielectric peak is suppressed and broadened. At the same time, the dielectric constant peak shifts to lower temperatures, allowing the sample to remain within the superparaelectric phase range at room temperature, which is beneficial for improving energy storage performance.

[0100] The unipolar hysteresis loops of the lead-free high-entropy relaxor ferroelectric materials prepared in Examples 1-2 and Comparative Examples 1-2 at room temperature and 10 Hz are as follows: Figure 4 As shown in the figure, the addition of a small amount of oxides improves the ceramic properties and significantly increases the breakdown field strength.

[0101] The energy storage density and energy storage efficiency of the lead-free high-entropy relaxor ferroelectric material prepared in Example 1 under different electric fields are as follows: Figure 5 As shown, under different electric field strengths, the energy storage density increases linearly while maintaining stable efficiency, achieving 13.5 J / cm². -3 It boasts excellent energy storage density and an ultra-high energy storage efficiency of 94.6%.

[0102] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A lead-free high-entropy relaxor ferroelectric material, characterized in that, The raw materials for the lead-free high-entropy relaxor ferroelectric material include ceramic powder and oxides; the general chemical formula of the ceramic powder is: (1-x)(Bi 0.2 Na 0.2 Ba 0.2 Sr 0.2 Ca 0.2 TiO3-xLa(Mg) 1 / 2 Zr 1 / 2 O3; Where x ranges from 0 to 0.

2.

2. The lead-free high-entropy relaxor ferroelectric material as described in claim 1, characterized in that, The oxides include MnO2, ZnO, Li2CO3 and Sm2O3; The mass of MnO2 is 0.3% to 0.7% of the mass of the ceramic powder raw material; The mass of ZnO is 0.05 to 0.2% of the mass of the ceramic powder raw material; The mass of Li2CO3 is 0.1% to 0.3% of the mass of the ceramic powder raw material; The mass of Sm2O3 is 0.1 to 0.22% of the mass of the ceramic powder raw material.

3. The lead-free high-entropy relaxor ferroelectric material as described in claim 1 or 2, characterized in that, The configurational entropy ΔS of the lead-free high-entropy relaxor ferroelectric material config ≥1.61R.

4. The method for preparing the lead-free high-entropy relaxor ferroelectric material according to any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Weigh the ceramic powder raw materials, mix them, and then pre-fire them to obtain ceramic powder; (2) The ceramic powder and oxide are mixed to obtain the casting slurry powder; (3) The cast slurry powder, solvent, dispersant, binder, plasticizer and homogenizer are mixed and then pressed, debinded and sintered in sequence to obtain the lead-free high entropy relaxation ferroelectric material.

5. The method for preparing lead-free high-entropy relaxor ferroelectric materials as described in claim 4, characterized in that, The ceramic powder raw materials mentioned in step (1) are Bi2O3, Na2CO3, BaCO3, SrCO3, CaCO3, La2O3, MgO, ZrO2 and TiO2; In step (1), the ball milling speed is 400-500 rpm and the ball milling time is 12-18 h; The target temperature for preheating in step (1) is 880-950℃, the target temperature for cooling is 800-870℃, the cooling rate is 5-10℃ / min, and the holding time after reaching the target temperature is 3-4h.

6. The method for preparing lead-free high-entropy relaxor ferroelectric materials as described in claim 5, characterized in that, The ball milling speed in step (2) is 500-650 rpm and the ball milling time is 10-12 h; the particle size of the cast slurry powder in step (2) is 150-250 mesh.

7. The method for preparing lead-free high-entropy relaxor ferroelectric materials as described in claim 6, characterized in that, The solvent mentioned in step (3) includes ethanol and methyl ethyl ketone; the mass of ethanol is 20-30% of the mass of the cast slurry powder; the mass of methyl ethyl ketone is 40-50% of the mass of the cast slurry powder. The dispersant mentioned in step (3) is one or more of castor oil, fish oil, phosphate esters and tributyl phosphate; The mass of the dispersant is 2-5% of the mass of the cast slurry powder.

8. The method for preparing lead-free high-entropy relaxor ferroelectric materials as described in claim 7, characterized in that, The adhesive mentioned in step (3) is one or more of polyvinyl butyral, polyvinyl alcohol, and methylcellulose; The mass of the binder is 8-10% of the mass of the cast slurry powder; The plasticizer mentioned in step (3) is one or more of polyethylene glycol, triethyl citrate, dibutyl sebacate and dibutyl phthalate; The mass of the plasticizer is 2.5% to 8% of the mass of the cast slurry powder; The homogenizer mentioned in step (3) is cyclohexanone; The mass of the homogenizer is 0.5 to 1.1% of the mass of the cast slurry powder.

9. The method for preparing lead-free high-entropy relaxor ferroelectric materials as described in claim 8, characterized in that, The pressing pressure in step (3) is 150-200 MPa, and the holding time is 10-15 min; The temperature for discharging adhesive in step (3) is 500-650℃, the heating rate is 0.3-1℃ / min, and the holding time is 4-7h.

10. The method for preparing lead-free high-entropy relaxor ferroelectric materials as described in claim 9, characterized in that, The sintering temperature in step (3) is 1180-1240℃, the heating rate is 1-5℃ / min, and the holding time is 2-4h.

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