A relaxor ferroelectric bulk material with both high energy storage density and high energy storage efficiency and a preparation method thereof

Abstract

The present invention discloses a relaxor ferroelectric bulk material with both high energy storage density and high energy storage efficiency and a preparation method thereof. Dry gel powder of NaNbO3, 80 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder, 200 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder and an additive are mixed and processed in a mass ratio of 0.06 - 0.10:1:1:1 to obtain a mixed powder; the mixed powder is made into a green body and then calcined to obtain a relaxor ferroelectric bulk material with both high energy storage density and high energy storage efficiency; the additive is at least one of BiFeO3, Na 0.5 Bi 0.5 TiO3 or (BiFeO3) 0.5 (Na 0.5 Bi 0.5 TiO3) 0.5 . The charge energy storage density of the relaxor ferroelectric bulk material prepared by the present invention is 1.91 - 3.22 J / cm 3 , the discharge energy storage density is 1.69 - 3.17 J / cm 3 , and the energy storage efficiency is 81.8 - 98.4%. It has both high energy storage density and high energy storage efficiency; the preparation method of the present invention also has the characteristics of small environmental pollution and high practicability, and has strong application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage bulk materials, and particularly relates to a relaxor ferroelectric bulk material with both high energy storage density and high energy storage efficiency and a preparation method thereof. Background Art

[0002] With the rapid development of the world economy and human society, people's demand for energy is increasing day by day. In particular, the standards and requirements for electric energy and its storage devices are constantly improving. Dielectric capacitors are suitable for high-power density fields such as medical, national defense, and space technology due to their ultra-high power density and ultra-fast charge and discharge capabilities. Among many dielectric capacitors, bulk material capacitors have medium breakdown field strength (BDS), low dielectric loss (tanδ), excellent temperature stability and anti-fatigue characteristics, and can better meet the requirements for energy storage materials in fields such as aerospace, oil drilling, and electromagnetic pulse weapons. At present, bulk material capacitors generally have the problems of small energy storage density and low energy storage efficiency. Developing new bulk material capacitors with both high energy storage density and high energy storage efficiency has important application value.

[0003] According to the classification, energy storage bulk material capacitors are divided into linear dielectrics, ferroelectrics, relaxor ferroelectrics, and antiferroelectrics. Common energy storage bulk materials include BaTiO3-based (BT-based), (Bi 0.5 Na 0.5 )TiO3-based (NBT-based), (K 0.5 Na 0.5 )NbO3-based (KNN-based), and AgNbO3-based (AN-based), etc. Some studies have provided energy storage bulk materials with high discharge energy storage density and high energy storage efficiency. For example, Patent CN 107935589 A discloses a trace zirconia-added ST-NBT energy storage ceramic and a preparation method thereof, and the discharge energy storage density of the ceramic reaches 2.84 J / cm 3 , and the energy storage efficiency reaches 71.5%; Patent CN107759217 A discloses a lead-free ceramic material with high energy storage density and high energy storage efficiency and a preparation method thereof, and the discharge energy storage density of the material reaches 1.73 J / cm 3 , and the energy storage efficiency reaches 90.1%; Patent CN 107244912 A discloses a new type of BCZT-based energy storage ceramic material, a preparation method thereof and an application, and the discharge energy storage density of the material reaches 0.66 J / cm 3 , and the energy storage efficiency reaches 88.1%; Patent CN 107459347A discloses a lead-free ceramic material with high energy storage density and high energy storage efficiency and a preparation method thereof, and the discharge energy storage density of the material reaches 1.98 J / cm 3, the energy storage efficiency reaches 90%; Patent CN106478097 A discloses a niobium silver-based lead-free antiferroelectric energy storage ceramic and a preparation method thereof, and the discharge energy storage density of the ceramic reaches 2.5 J / cm 3 , and the energy storage efficiency reaches 57.2%.

[0004] Among these bulk material capacitors, relaxor ferroelectrics have a "slender" ferroelectric hysteresis loop and high dielectric temperature stability, and have great advantages in the field of energy storage. However, there is still room for improvement in the energy storage density and energy storage efficiency of these materials. Research shows that using additives is an effective method without significantly reducing the dielectric constant, and the energy storage density can be increased by increasing the breakdown strength.

[0005] However, which additives to use, the ratio of additives, and the influence of the introduction of additives on the microscopic morphology of the material are extremely important factors that directly affect the performance of the relaxor ferroelectric bulk energy storage material. Therefore, it is important to provide a simple and effective method for preparing relaxor ferroelectric bulk materials with both high energy storage density and high energy storage efficiency using additives. Summary of the Invention

[0006] To solve the technical problems existing in the prior art, the present invention provides a relaxor ferroelectric bulk material with both high energy storage density and high energy storage efficiency and a preparation method thereof. By adjusting the ratio of additives, the relaxor ferroelectric bulk material prepared by the present invention has excellent energy storage density and energy storage efficiency, and the charge energy storage density is 1.91 - 3.22 J / cm 3 , the discharge energy storage density is 1.69 - 3.17 J / cm 3 , and the energy storage efficiency is 81.8 - 98.4%; in addition, the preparation method of the present invention also has the characteristics of small environmental pollution and high practicability.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A preparation method of a relaxor ferroelectric bulk material with both high energy storage density and high energy storage efficiency, the method comprising:

[0009] Mixing and processing NaNbO3 dry gel powder, Ba with different particle sizes 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder and additives to obtain a mixed powder;

[0010] Making the mixed powder into a green body and then calcining to obtain a relaxor ferroelectric bulk material with both high energy storage density and high energy storage efficiency.

[0011] Further, the different particle sizes of Ba 0.7 Sr0.3 Zr 0.2 Ti 0.8 The particle sizes of O3@NaNbO3 powder are 80 nm and 200 nm;

[0012] The mass ratio of the NaNbO3 xerogel powder, 80 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 The mass ratio of the O3@NaNbO3 powder, 200 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 The mass ratio of the O3@NaNbO3 powder and the additive is 0.06 - 0.10:1:1:1.

[0013] Furthermore, the additive is at least one of BiFeO3, Na 0.5 Bi 0.5 TiO3 or (BiFeO3) 0.5 (Na 0.5 Bi 0.5 TiO3) 0.5 among them.

[0014] Furthermore, the additive is BiFeO3 and Na 0.5 Bi 0.5 TiO3, and the mass ratio is 1:1.

[0015] Furthermore, the preparation method of the BiFeO3 is as follows:

[0016] Weigh Bi2O3 and Fe2O3 according to the stoichiometric ratio, mix, ball-mill, dry and calcine them to obtain BiFeO3;

[0017] The Na 0.5 Bi 0.5 The preparation method of TiO3 is as follows:

[0018] Weigh Na2CO3, Bi2O3 and TiO2 according to the stoichiometric ratio, mix, ball-mill, dry and calcine them to obtain Na 0.5 Bi 0.5 TiO3;

[0019] The preparation method of the (BiFeO3) 0.5 (Na 0.5 Bi 0.5 TiO3) 0.5 is as follows:

[0020] Weigh Bi2O3, Fe2O3, Na2CO3 and TiO2 according to the stoichiometric ratio, mix, ball-mill, dry and calcine them to obtain (BiFeO3)0.5 (Na 0.5 Bi 0.5 TiO3) 0.5 。

[0021] Furthermore, the preparation method of the NaNbO3 xerogel powder is as follows:

[0022] Weigh water-soluble niobium salt and water-soluble sodium salt according to the stoichiometric ratio. Mix the water-soluble niobium salt with water to prepare a niobium salt aqueous solution. Add the water-soluble sodium salt to the niobium salt aqueous solution, adjust the pH and then raise the temperature for reaction to obtain NaNbO3 gel; evaporate the water in the gel to obtain NaNbO3 xerogel powder;

[0023] Among them, the dosage of the water-soluble sodium salt is determined by the water-soluble niobium salt, and every 0.008 - 0.015 mol of water-soluble niobium salt is mixed with 40 - 60 mL of water;

[0024] The pH adjustment is to adjust the pH to 6.5 - 8.0 with ammonia water.

[0025] Furthermore, the preparation methods of 80 nm and 200 nm of nano Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder are as follows:

[0026] Weigh 70 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3, add it to the NaNbO3 gel, raise the temperature and stir for reaction, then calcine the mixture to obtain 80 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder;

[0027] Weigh 190 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3, add it to the NaNbO3 gel, raise the temperature and stir for reaction, then calcine the mixture to obtain 200 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder.

[0028] Furthermore, 70 nm and 190 nm of Ba 0.7 Sr 0.3 Zr 0.2 Ti0.8 The preparation methods of O3 are as follows:

[0029] Weigh barium salt, strontium salt, zirconium salt and titanium salt according to the stoichiometric ratio, mix the barium salt, strontium salt, zirconium salt and titanium salt, add 16 mol / L sodium hydroxide aqueous solution, then raise the temperature and stir for reaction, let it stand, wash, filter and collect the insoluble matter for drying to obtain 70 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3 powder; wherein, the barium salt, strontium salt, zirconium salt and titanium salt are all water-soluble, the amounts of the strontium salt, zirconium salt and titanium salt are determined by the barium salt, and 80 - 150 mL of 16 mol / L sodium hydroxide aqueous solution is added for every 0.005 - 0.015 mol of barium salt;

[0030] Weigh barium salt, strontium salt, zirconium salt and titanium salt according to the stoichiometric ratio, mix the barium salt, strontium salt, zirconium salt and titanium salt, add 8 mol / L sodium hydroxide aqueous solution, then raise the temperature and stir for reaction, let it stand, wash, filter and collect the insoluble matter for drying to obtain 190 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3 powder; wherein, the barium salt, strontium salt, zirconium salt and titanium salt are all water-soluble, the amounts of the strontium salt, zirconium salt and titanium salt are determined by the barium salt, and 80 - 150 mL of 8 mol / L sodium hydroxide aqueous solution is added for every 0.005 - 0.015 mol of barium salt.

[0031] Further, the preparation method of the NaNbO3 gel is as follows:

[0032] Weigh water-soluble niobium salt and water-soluble sodium salt according to the stoichiometric ratio, mix the water-soluble niobium salt with water to prepare a niobium salt aqueous solution, add the water-soluble sodium salt to the niobium salt aqueous solution, adjust the pH and then raise the temperature for reaction to obtain the NaNbO3 gel;

[0033] Among them, the amount of the water-soluble sodium salt is determined by the water-soluble niobium salt, and 40 - 60 mL of water is mixed with every 0.008 - 0.015 mol of water-soluble niobium salt;

[0034] The pH adjustment is to adjust the pH to 6.5 - 8.0 with ammonia water.

[0035] Further, the temperature-raising and stirring reaction is specifically as follows:

[0036] Raise the temperature to 50 - 100 °C;

[0037] Stir and react at a rotation speed of 200 - 500 rpm for 3 - 6 h.

[0038] Further, the mixing treatment is specifically:

[0039] NaNbO3 powder, Ba with different particle sizes 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder and an additive are mixed to form a mixture. The mixture is ball-milled in absolute ethanol and then dried to obtain a mixed powder.

[0040] The present invention also provides a relaxor ferroelectric bulk material with both high energy storage density and high energy storage efficiency. The material includes:

[0041] NaNbO3 xerogel powder, 80nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder, 200nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder and an additive;

[0042] The material is obtained by mixing and processing NaNbO3 xerogel powder, 80nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder, 200nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder and an additive to obtain a mixed powder. The mixed powder is made into a green body and then calcined to obtain a relaxor ferroelectric bulk material with both high energy storage density and high energy storage efficiency.

[0043] Furthermore, the mass ratio of the NaNbO3 xerogel powder, 80nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder, 200nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder and the additive is 0.06 - 0.10:1:1:1;

[0044] The additive is BiFeO3, Na 0.5 Bi 0.5 TiO3 or (BiFeO3) 0.5 (Na 0.5 Bi 0.5TiO3) 0.5 At least one of the following.

[0045] Furthermore, the additive is BiFeO3 and Na 0.5 Bi 0.5 TiO3, and the mass ratio is 1:1.

[0046] Furthermore, the relative density of the material is 0.96 - 0.98, and the grain size is 190 - 233 nm;

[0047] The charge storage density of the material is 1.91 - 3.22 J / cm 3 , and the discharge storage density is 1.69 - 3.17 J / cm 3 , and the energy storage efficiency is 81.8 - 98.4%.

[0048] The present invention has the following beneficial effects compared with the prior art:

[0049] (1) The nano-powders prepared by the present invention are in the micro-nano scale, which is beneficial to improving the breakdown strength of the prepared relaxor ferroelectric bulk material;

[0050] (2) BiFeO3 and Na added in specific proportions in the present invention 0.5 Bi 0.5 TiO3 can form a solid solution with NaNbO3 and Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3, Nb 5+ substitutes for Ti 4+ , forming B-site substitution, breaking its long-range ordered structure, promoting the formation of nano-domains, and helping to improve the polarization difference; Nb 5+ has better chemical stability and a larger band gap, which is beneficial to reducing dielectric loss, thereby improving the breakdown strength and increasing the energy storage density.

[0051] (3) The present invention has the advantage of being able to prepare lead-free bulk materials with high comprehensive energy storage performance, and has the advantages of high performance, pollution-free, environmental protection, etc. It can be used for the production of a new generation of energy storage bulk materials to meet the needs of the environmental protection and energy fields. Brief Description of the Drawings

[0052] Figure 1 SEM image of the relaxor ferroelectric bulk material prepared in Example 1 of the present invention;

[0053] Figure 2 SEM image of the relaxor ferroelectric bulk material prepared in Example 2 of the present invention;

[0054] Figure 3SEM image of the relaxor ferroelectric bulk material prepared in Example 3 of the present invention;

[0055] Figure 4 SEM image of the relaxor ferroelectric bulk material prepared in Example 4 of the present invention;

[0056] Figure 5 SEM image of the relaxor ferroelectric bulk material prepared in the comparative example of the present invention;

[0057] Figure 6 XRD pattern of the relaxor ferroelectric bulk material prepared in Examples 1-4 of the present invention;

[0058] Figure 7 Electric hysteresis loop of the relaxor ferroelectric bulk material prepared in Examples 1-4 of the present invention;

[0059] Figure 8 Comparison chart of the charge storage density, discharge storage density and storage efficiency of the relaxor ferroelectric bulk material prepared in Examples 1-4 of the present invention. Detailed implementation manners

[0060] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention and the accompanying drawings of the specification. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0061] It should be noted that the preparation methods of some raw materials used in the specific embodiments of the present invention are described here. Unless otherwise specified, these raw materials used in the embodiments are prepared by the following methods without further treatment. The mentioned raw material preparation methods will not be repeated in the specific embodiments.

[0062] Preparation method of NaNbO3 dry gel powder:

[0063] Weigh 0.01 mol of niobium citrate and 0.005 mol of sodium carbonate according to the stoichiometric ratio; mix the niobium citrate with 50 mL of deionized water to prepare an aqueous solution of niobium citrate under stirring at a rotation speed of 300 rpm; under stirring at a rotation speed of 300 rpm, add the sodium carbonate to the aqueous solution of niobium citrate, adjust the pH of the solution to 7.0 with ammonia water, raise the temperature to 60 °C and stir for 4 h to obtain NaNbO3 gel, and evaporate the water in the gel to obtain NaNbO3 dry gel powder.

[0064] 70nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8Preparation method of O3 powder:

[0065] Weigh 0.007 mol of Ba(CH3COOH)2, 0.003 mol of Sr(CH3COOH)2, 0.002 mol of Zr(NO3)4 and 0.008 mol of TiCl4 according to the stoichiometric ratio. Mix the Ba(CH3COOH)2, Sr(CH3COOH)2, Zr(NO3)4 and TiCl4, add 100 mL of sodium hydroxide aqueous solution with a concentration of 16 mol / L, heat up to 80 °C and stir for 4 h. Stop heating and stirring, let it stand for 12 h, wash, filter and collect the insoluble matter, and place it in an oven at 100 °C for constant temperature drying for 8 h to obtain 70 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3 powder.

[0066] 190 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 Preparation method of O3 powder:

[0067] Weigh 0.007 mol of Ba(CH3COOH)2, 0.003 mol of Sr(CH3COOH)2, 0.002 mol of Zr(NO3)4 and 0.008 mol of TiCl4 according to the stoichiometric ratio. Mix the Ba(CH3COOH)2, Sr(CH3COOH)2, Zr(NO3)4 and TiCl4, add 100 mL of sodium hydroxide aqueous solution with a concentration of 8 mol / L, then heat up to 80 °C and stir for 4 h. Stop heating and stirring, let it stand for 12 h, wash, filter and collect the insoluble matter, and place it in an oven at 100 °C for constant temperature drying for 8 h to obtain 190 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3 powder.

[0068] 80 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 Preparation method of O3@NaNbO3 powder:

[0069] Weigh 0.01 mol of niobium citrate and 0.005 mol of sodium carbonate according to the stoichiometric ratio; mix the niobium citrate with 50 mL of deionized water under stirring at a rotation speed of 300 rpm to prepare an aqueous solution of niobium citrate, add the sodium carbonate to the aqueous solution of niobium citrate, adjust the pH of the solution to 7.0 with ammonia water, heat up to 60 °C and stir for 4 h to obtain NaNbO3 gel;

[0070] Weigh 70 nm Ba according to the stoichiometric ratio 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3 powder, add it to the NaNbO3 gel under stirring at a rotation speed of 300 rpm, heat up to 60 °C and stir for reaction for 4 h to obtain a mixture, and calcine the mixture at 800 °C for 2 h to obtain 80 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder

[0071] The preparation method of 200 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder:

[0072] Weigh 0.01 mol niobium citrate and 0.005 mol sodium carbonate according to the stoichiometric ratio; mix the niobium citrate with 50 mL of deionized water under stirring at a rotation speed of 300 rpm to prepare an aqueous solution of niobium citrate; under stirring at a rotation speed of 300 rpm, add the sodium carbonate to the aqueous solution of niobium citrate, adjust the pH of the solution to 7.0 with ammonia water, heat up to 60 °C and stir for reaction for 4 h to obtain a NaNbO3 gel

[0073] Weigh 190 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3 powder, add it to the NaNbO3 gel under stirring at a rotation speed of 300 rpm, heat up to 60 °C and stir for reaction for 4 h to obtain a mixture, and calcine the mixture at 800 °C for 2 h to obtain 200 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder

[0074] The preparation method of BiFeO3 is as follows:

[0075] Weigh Bi2O3 and Fe2O3 according to the stoichiometric ratio, place Bi2O3 and Fe2O3 in a ball mill, keep ball milling for 24 h at a ball milling speed of 100 r / min, collect the sample, place it in an oven at 105 °C for 12 h until it is dried to obtain a powder, and calcine the powder at 800 °C for 2 h to obtain BiFeO3

[0076] Na 0.5 Bi 0.5 The preparation method of Na

[0077] Weigh Na2CO3, Bi2O3 and TiO2 according to the stoichiometric ratio. Place Na2CO3, Bi2O3 and TiO2 in a ball mill. Keep ball milling for 24 h at a ball milling speed of 100 r / min. Collect the sample and place it in an oven at 105 °C for 12 h until dried to obtain a powder. Calcinate the powder at 800 °C for 2 h to obtain Na 0.5 Bi 0.5 TiO3.

[0078] The preparation method of the (BiFeO3) 0.5 (Na 0.5 Bi 0.5 TiO3) 0.5 is as follows:

[0079] Weigh Bi2O3, Fe2O3, Na2CO3 and TiO2 according to the stoichiometric ratio. Place Bi2O3, Fe2O3, Na2CO3 and TiO2 in a ball mill. Keep ball milling for 24 h at a ball milling speed of 100 r / min. Collect the sample and place it in an oven at 105 °C for 12 h until dried to obtain a powder. Calcinate the powder at 800 °C for 2 h to obtain (BiFeO3) 0.5 (Na 0.5 Bi 0.5 TiO3) 0.5 .

[0080] It should be noted that some metal salts used in the above raw material preparation methods are not limited to the listed Ba(CH3COOH)2, Sr(CH3COOH)2, Zr(NO3)4, TiCl4, niobium citrate and sodium carbonate, and can be water-soluble metal salts that meet the preparation conditions. The amounts of metal salts used are not limited to the listed amounts and can be enlarged or reduced according to the stoichiometric ratio. In actual preparation, since the chemical formula of the product is determined, all raw materials can be determined by one raw material. For example, to prepare Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3 powder, the amounts of strontium salt, zirconium salt and titanium salt are determined by the barium salt, and 80 - 150 mL of 16 mol / L sodium hydroxide aqueous solution is added to every 0.005 - 0.015 mol of barium salt; to prepare NaNbO3 gel, the amount of water-soluble sodium salt is determined by the water-soluble niobium salt, and every 0.008 - 0.015 mol of water-soluble niobium salt is mixed with 40 - 60 mL of water.

[0081] Some abbreviations that may be used in the examples and drawings are as follows:

[0082] BSZT, Ba 0.7 Sr 0.3Zr 0.2 Ti 0.8 O3;

[0083] NN, NaNbO3;

[0084] BSZT@NN, Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3;

[0085] BF, BiFeO3;

[0086] NBT, Na 0.5 Bi 0.5 TiO3;

[0087] (BF) 0.5 (NBT) 0.5 , (BiFeO3) 0.5 (Na 0.5 Bi 0.5 TiO3) 0.5 .

[0088] Example 1

[0089] A relaxor ferroelectric bulk material with both high energy storage density and high energy storage efficiency, and its preparation method is as follows:

[0090] Weigh 0.8 g of NaNbO3 xerogel powder, 10.0 g of 80 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder, 10.0 g of 200 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder, 5 g of BiFeO3 and 5 g of Na 0.5 Bi 0.5 TiO3, mix to form a mixture; ball-mill the mixture in absolute ethanol at a ball-milling speed of 100 r / min for 24 h to mix evenly, and then place it in a constant-temperature oven at 90 °C to dry for 12 h to obtain a mixed powder;

[0091] Weigh 10 g of the mixed powder, granulate and press it into a green body, and sinter the green body at 1100 °C for 4 h to obtain a circular disc bulk material sample, which is a relaxor ferroelectric bulk material with both high energy storage density and high energy storage efficiency, named BSZT@NN-BF-NBT.

[0092] Example 2

[0093] A relaxor ferroelectric bulk material with both high energy storage density and high energy storage efficiency, and its preparation method is as follows:

[0094] Weigh 0.8 g of NaNbO3 xerogel powder, 10.0 g of 80 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder, 10.0 g of 200 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder and 10 g of (BiFeO3) 0.5 (Na 0.5 Bi 0.5 TiO3) 0.5 , mix to form a mixture; ball-mill the mixture in absolute ethanol at a ball-milling speed of 100 r / min for 24 h to mix evenly, and then place it in a constant-temperature oven at 90 °C to dry for 12 h to obtain a mixed powder;

[0095] Weigh 10 g of the mixed powder, granulate and press it into a green body, sinter the green body at 1100 °C for 4 h to obtain a circular disc bulk material sample, which is a relaxor ferroelectric bulk material with both high energy storage density and high energy storage efficiency, named BSZT@NN-(BF) 0.5 (NBT) 0.5 .

[0096] Example 3

[0097] A relaxor ferroelectric bulk material with both high energy storage density and high energy storage efficiency, and its preparation method is as follows:

[0098] Weigh 0.8 g of NaNbO3 xerogel powder, 10.0 g of 80 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder, 10.0 g of 200 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder and 10 g of BiFeO3, mix to form a mixture; ball-mill the mixture in absolute ethanol at a ball-milling speed of 100 r / min for 24 h to mix evenly, and then place it in a constant-temperature oven at 90 °C to dry for 12 h to obtain a mixed powder;

[0099] Weigh 10 g of the mixed powder, granulate and press it into a green body, sinter the green body at 1100 °C for 4 h to obtain a wafer bulk material sample, which is a relaxor ferroelectric bulk material with both high energy storage density and high energy storage efficiency, named BSZT@NN-BF.

[0100] Example 4

[0101] A relaxor ferroelectric bulk material with both high energy storage density and high energy storage efficiency, and its preparation method is as follows:

[0102] Weigh 0.8 g of NaNbO3 dry gel powder, 10.0 g of 80 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder, 10.0 g of 200 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder and 10 g of Na 0.5 Bi 0.5 TiO3, mix to form a mixture; ball-mill the mixture in absolute ethanol at a ball-milling speed of 100 r / min for 24 h to mix evenly, and then place it in a constant-temperature oven at 90 °C to dry for 12 h to obtain a mixed powder;

[0103] Weigh 10 g of the mixed powder, granulate and press it into a green body, sinter the green body at 1100 °C for 4 h to obtain a wafer bulk material sample, which is a relaxor ferroelectric bulk material with both high energy storage density and high energy storage efficiency, named BSZT@NN-NBT.

[0104] Comparative Example 1

[0105] A relaxor ferroelectric bulk material, and its preparation method is as follows:

[0106] Weigh 0.8 g of NaNbO3 dry gel powder, 10.0 g of 80 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder and 10.0 g of 200 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder, mix to form a mixture; ball-mill the mixture in absolute ethanol at a ball-milling speed of 100 r / min for 24 h to mix evenly, and then place it in a constant-temperature oven at 90 °C to dry for 12 h to obtain a mixed powder;

[0107] Weigh 10 g of the mixed powder, granulate and press it into a green body. Sinter the green body at 1100 °C for 4 h to obtain a disc-shaped bulk material sample, which is the relaxor ferroelectric bulk material, named BSZT@NN.

[0108] Test example

[0109] The morphologies of the relaxor ferroelectric bulk materials prepared in Examples 1-4 and the comparative example of the present invention were analyzed by SEM. The SEM characterization results of Examples 1-4 and the comparative example are respectively as Figures 1 - 5 shown. From Figure 1 it can be seen that BSZT@NN-BF-NBT has a uniform morphology, presenting a spherical shape as a whole, and there are no obvious agglomerations and large blocky particles. The grain size is concentrated at 200 nm. This may be because BiFeO3 and Na 0.5 Bi 0.5 TiO3 added in a specific ratio react more stably with other raw materials in the mixed powder during sintering and can form a good solid solution state. Figure 2 of BSZT@NN-(BF) 0.5 (NBT) 0.5 structures have many large blocks with different particle sizes (diameter greater than 800 nm). The shapes of the large blocks are not uniform. This may be because the added (BiFeO3) 0.5 (Na 0.5 Bi 0.5 TiO3) 0.5 react more violently at the initial stage of sintering, resulting in the rapid formation of massive particles. The morphology of BSZT@NN-BF( Figure 3 shown) is similar to that of BSZT@NN-(BF) 0.5 (NBT) 0.5 structures, and there are also crack-like structures. This may be because the addition of BiFeO3 makes other raw materials in the mixed powder prone to agglomeration during sintering, which is related to the high sintering activity of BiFeO3. The morphology of BSZT@NN-NBT is as Figure 4 shown. It can be seen that its structure is relatively uniform, with a large number of spherical fine particles, but there are also agglomerated spherical particles with a diameter exceeding 800 nm. This may be because the addition of Na 0.5 Bi 0.5 TiO3 reacts slowly and uniformly at the initial stage of sintering, but after forming a solid solution state in the later stage, the reaction rate becomes faster, causing some small particles to agglomerate. The morphology of the material prepared without adding additives is as Figure 5 shown. It can be seen that the BSZT@NN structure has some pores, presenting a random distribution of large particles (diameter greater than 800 nm) with many small particles (diameter less than 50 nm). This may be due to the poor sintering performance of BSZT@NN. From the SEM characterization results, it can be seen that the additives BiFeO3, Na0.5 Bi 0.5 TiO3, (BiFeO3) 0.5 (Na 0.5 Bi 0.5 TiO3) 0.5 or BiFeO3 / Na 0.5 Bi 0.5 TiO3 can improve the performance of BSZT@NN and regulate the microstructure of the material.

[0110] In addition, the average grain size of the relaxor ferroelectric bulk materials in Examples 1-4 and the comparative examples as counted by SEM is shown in Table 1. From the statistical results in Table 1, it can be seen that the grain size observed by SEM in Example 1 is the closest to the counted grain size, further demonstrating the uniformity of the morphology of BSZT@NN-BF-NBT prepared in Example 1.

[0111] Table 1 Average grain size of the relaxor ferroelectric bulk materials in Examples 1-4 and the comparative examples as counted by SEM

[0112] Average grain size (nm) Example 1 190 Example 2 216 Example 3 233 Example 4 204 Comparative example 400

[0113] Research shows that the microstructure grain size of the material can affect the breakdown strength of the material, thus effectively increasing the energy storage density. Uniform and smaller grain sizes contribute to improving the breakdown strength of the material. In Example 1 of the present invention, by using BiFeO3 and Na 0.5 Bi 0.5 TiO3 as additives, the prepared BSZT@NN-BF-NBT has a suitable morphology and may have higher energy storage potential.

[0114] In addition, the relative densities of the relaxor ferroelectric bulk materials in Examples 1-4 and the comparative examples of the present invention were also tested, and the results are shown in Table 2. It can be seen that the relative densities of each material are close, among which the relative density of BSZT@NN-BF-NBT is the largest at 0.98. A larger relative density has a higher resistance to electrical breakdown; since the ceramic pores and defects are fewer for a larger relative density, the sample has a higher resistance to thermal breakdown and fatigue; the combined effect of the two can effectively increase the breakdown field strength of the ceramic, thereby further improving the energy storage performance of the ceramic.

[0115] Table 2 Relative densities of the relaxor ferroelectric bulk materials in Examples 1-4 and the comparative examples

[0116] Relative density Example 1 0.98 Example 2 0.97 Example 3 0.97 Example 4 0.96 Comparative example 0.95

[0117] The XRD test results of the relaxor ferroelectric bulk materials prepared in Examples 1-4 are as Figure 6As shown. The diffraction peaks (100), (110), (111), (200), (210), (211), and (220) in the figure correspond to the typical perovskite structure. From Figure 6 It can be seen that the diffraction peak positions of the materials BSZT@NN-BF-NBT, BSZT@NN-(BF) 0.5 (NBT) 0.5 , BSZT@NN-BF, and BSZT@NN-NBT prepared in the embodiments of the present invention are generally similar, indicating that a perovskite structure solid solution has been successfully prepared; the presence of other impurity peaks is not observed, indicating that the materials prepared in the present invention have high purity. It should be noted that Figure 6 On the right is the detailed view of the (200) diffraction peak of each material at a diffraction angle of 44-47°, indicating that the obtained samples are perovskite structures in a pseudo-cubic phase. This structure is because the solid solution process of the nano-additive breaks the long-range ordered structure, promotes the formation of nano-domains, and helps to improve the polarization difference.

[0118] The sintered samples were processed into thin slices with smooth surfaces on both sides and a thickness of about 0.2 mm, gold electrodes were plated, and their ferroelectric properties were tested at 25 °C and a frequency of 10 Hz. The results are as Figure 7 shown. From Figure 7 the ferroelectric hysteresis loops of the relaxor ferroelectric bulk materials prepared in Examples 1-4 of the present invention, it can be seen that the maximum polarization intensities P 0.5 (NBT) 0.5 of the BSZT@NN-BF-NBT, BSZT@NN-(BF) m samples are 16.90 μC / cm 2 , 15.00 μC / cm 2 , 15.50 μC / cm 2 , and 12.00 μC / cm 2 , respectively, and the corresponding remanent polarization intensities P r are 0.05 μC / cm 2 , 0.97 μC / cm 2 , 1.21 μC / cm 2 , and 0.92 μC / cm 2 . The polarization differences ΔP of the four samples are all higher than 11.00 μC / cm 2 . The BSZT@NN-BF-NBT sample has the highest ΔP (16.85 μC / cm 2 ), which may be related to the generation of polymorphic nano-domains. Although the P r of the BSZT@NN-NBT sample is lower, the non-uniform morphology reduces the P m of the system. On the contrary, although the P mis relatively high, but P r is also relatively high, resulting in a somewhat reduced ΔP. BSZT@NN-(BF) 0.5 (NBT) 0.5 The ΔP of the sample is second only to that of the BSZT@NN-BF-NBT sample, which is related to their similar components. At a high electric field of 290 kV / cm, the polarization hysteresis loops of all four samples are "slender" quasi-linear, indicating that the samples have obvious relaxation characteristics. Among them, the BSZT@NN-BF-NBT sample has the most "slender" polarization hysteresis loop, very close to a straight line, indicating that the sample has a high relaxation characteristic and the largest W rec and η values.

[0119] Figure 8 Figure 12 is a comparison chart of the charging energy density, discharging energy density, and efficiency curves of the relaxor ferroelectric bulk materials prepared in Examples 1 to 4 of the present invention. Figure 7 and Figure 8 The performance indexes of the relaxor ferroelectric bulk materials in Examples 1 to 4 summarized from the results of

[0120] Table 3 shows the performance indexes of the relaxor ferroelectric bulk materials in Examples 1 to 4 and the comparative example. The table also summarizes the results of the relaxor ferroelectric bulk materials of the comparative example under the same test conditions.

[0121]

[0122]

[0123] In practical applications, as an energy storage functional ceramic material, not only a high energy storage density is required, but also a high energy storage efficiency should be possessed. A low energy storage efficiency will cause a large amount of energy to be converted into heat. A higher breakdown strength can broaden the application range of the material. As can be seen from the results in Table 3, the W rec of the comparative example without adding additives is only 0.83 J / cm 3 . The BSZT@NN-(BF) 0.5 (NBT) 0.5 sample in Example 2 shows good energy storage performance, and the W rec reaches 2.25 J / cm 3 , and the corresponding η is 84.6%. The W rec of the BSZT@NN-BF-NBT sample in Example 3 and the BSZT@NN-BF sample in Example 4 are 2.11 J / cm 3 and 1.69 J / cm 3 respectively, and the corresponding η are 81.8% and 88.5% respectively.

[0124] It should be noted that the relaxor ferroelectric bulk material in Embodiment 1 of the present invention has the best performance, with a discharge density reaching 3.17 / cm 3 , a storage efficiency as high as 98.4%, and a breakdown field strength as high as 354 kV / cm. Combining the SEM and XRD results, this may be because by using BiFeO3 and Na 0.5 Bi 0.5 TiO3 as additives applied to Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 and NaNbO3 mixed powders for sintering can effectively control the progress of the sintering reaction, enabling NaNbO3 to form a solid solution with Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3, Nb 5+ substitutes for Ti 4+ , forming B-site substitution, breaking its long-range ordered structure, promoting the formation of nano-domains, and contributing to improving the polarization difference; Nb 5+ has better chemical stability and a larger bandgap, which is beneficial to reducing dielectric loss, thereby increasing the breakdown strength and improving the energy storage density. Generally speaking, the BSZT@NN-BF-NBT sample prepared in the embodiment has the best energy storage performance because the BSZT@NN-BF-NBT sample can make the trigonal, tetragonal, and cubic phases have a gradient distribution, obtaining multi-state nano-domains, making the free energy distribution of the system more flat, being more responsive to the external electric field, being able to bear more voltage, and the higher breakdown strength also improves W rec and η.

[0125] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of a relaxor ferroelectric bulk material with both high energy storage density and high energy storage efficiency, characterized in that, The method includes: Mix the NaNbO3 dry gel powder, Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder with different particle sizes and an additive to obtain a mixed powder; the mass ratio of the NaNbO3 dry gel powder, Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder with different particle sizes and the additive is 0.06 - 0.10:1:1:1; the additive is at least one of BiFeO3, Na 0.5 Bi 0.5 TiO3 or (BiFeO3) 0.5 (Na 0.5 Bi 0.5 TiO3) 0.5 ; After making the mixed powder into a green body and then calcining it, a relaxor ferroelectric bulk material with both high energy storage density and high energy storage efficiency is obtained.

2. The preparation method according to claim 1, characterized in that, The Ba with different particle sizes 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powders are 80 nm and 200 nm; The NaNbO3 xerogel powder, 80nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder, 200nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 The mass ratio of O3@NaNbO3 powder and the additive is 0.06 - 0.10:1:1:

1.

3. The preparation method according to claim 2, characterized in that, The additive is BiFeO3 and Na 0.5 Bi 0.5 TiO3, and the mass ratio is 1:

1.

4. The preparation method according to claim 2, wherein The preparation method of the BiFeO3 is as follows: Weigh Bi2O3 and Fe2O3 according to the stoichiometric ratio, mix, ball-mill, dry, and calcine them to obtain BiFeO3; The described Na 0.5 Bi 0.5 The preparation method of TiO3 is as follows: Weigh Na2CO3, Bi2O3 and TiO2 according to the stoichiometric ratio. After mixing, ball milling, drying and calcination, we obtain Na 0.5 Bi 0.5 TiO3; The (BiFeO3) 0.5 (Na 0.5 Bi 0.5 TiO3) 0.5 The preparation method is as follows: Weigh Bi2O3, Fe2O3, Na2CO3 and TiO2 according to the stoichiometric ratio. After mixing, ball milling, drying and calcination, (BiFeO3) is obtained 0.5 (Na 0.5 Bi 0.5 TiO3) 0.5 .

5. The preparation method according to claim 2, characterized in that, The preparation method of the NaNbO3 dry gel powder is as follows: Weigh a water-soluble niobium salt and a water-soluble sodium salt according to the stoichiometric ratio. Mix the water-soluble niobium salt with water to prepare a niobium salt aqueous solution. Add the water-soluble sodium salt to the niobium salt aqueous solution, adjust the pH, and then raise the temperature for reaction to obtain a NaNbO3 gel; evaporate the moisture of the gel to obtain the NaNbO3 dry gel powder; Among them, the amount of the water-soluble sodium salt is determined by the water-soluble niobium salt, and every 0.008 - 0.015 mol of the water-soluble niobium salt is mixed with 40 - 60 mL of water; The adjustment of the pH is to adjust the pH to 6.5 - 8.0 with ammonia water.

6. The preparation method according to claim 2, characterized in that, Nano Ba of 80nm and 200nm 0.7 Sr 0.3 Zr 0.2 Ti 0.8 The preparation methods of O3@NaNbO3 powder are as follows: Weigh 70 nm Ba in stoichiometric ratio 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3, add it to the NaNbO3 gel, calcine the mixture after heating and stirring the reaction, and obtain 80 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder Weigh 190 nm Ba in stoichiometric ratio 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3, add it to the NaNbO3 gel, heat up and stir the reaction, then calcine the mixture to obtain 200 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder.

7. The preparation method according to claim 6, wherein 70nm and 190nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 The preparation methods of O3 are as follows: Weigh barium salt, strontium salt, zirconium salt and titanium salt according to the stoichiometric ratio, mix the barium salt, strontium salt, zirconium salt and titanium salt, add 16 mol / L sodium hydroxide aqueous solution, then raise the temperature and stir for reaction, let it stand, wash, filter and collect the insoluble matter for drying to obtain 70 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3 powder; wherein, the barium salt, strontium salt, zirconium salt and titanium salt are all water-soluble, the amounts of the strontium salt, zirconium salt and titanium salt are determined by the barium salt, and 80-150 mL of 16 mol / L sodium hydroxide aqueous solution is added for every 0.005-0.015 mol of barium salt; Weigh barium salt, strontium salt, zirconium salt and titanium salt according to stoichiometric ratio, mix the barium salt, strontium salt, zirconium salt and titanium salt, add an 8 mol / L aqueous sodium hydroxide solution, then raise the temperature and stir for reaction, let it stand, wash, filter and collect the insoluble matter for drying to obtain 190 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3 powder; wherein, the barium salt, strontium salt, zirconium salt and titanium salt are all water-soluble, the dosages of the strontium salt, zirconium salt and titanium salt are determined by the barium salt, and 80-150 mL of 8 mol / L aqueous sodium hydroxide solution is added for every 0.005-0.015 mol of barium salt.

8. The preparation method according to claim 6, characterized in that, The preparation method of the NaNbO3 gel is as follows: Weigh a water-soluble niobium salt and a water-soluble sodium salt according to the stoichiometric ratio. Mix the water-soluble niobium salt with water to prepare a niobium salt aqueous solution. Add the water-soluble sodium salt to the niobium salt aqueous solution, adjust the pH, and then raise the temperature for reaction to obtain a NaNbO3 gel; Among them, the amount of the water-soluble sodium salt is determined by the water-soluble niobium salt, and every 0.008 - 0.015 mol of the water-soluble niobium salt is mixed with 40 - 60 mL of water; The adjustment of the pH is to adjust the pH to 6.5 - 8.0 with ammonia water.

9. The preparation method according to claim 5 or 7 or 8, characterized in that, The specific process of the temperature-raising stirring reaction is as follows: Raise the temperature to 50 - 100 °C; Stir and react at a rotation speed of 200 - 500 rpm for 3 - 6 h.

10. The preparation method according to claim 1, wherein The specific process of the mixing treatment is as follows: NaNbO3 powder, Ba with different particle sizes 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder and additives are mixed to form a mixture, and the mixture is ball-milled in absolute ethanol and then dried to obtain a mixed powder.

11. A relaxor ferroelectric bulk material with both high energy storage density and high energy storage efficiency, characterized in that, The material includes: NaNbO3 dry gel powder, 80nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder, 200nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder and additives; The material is obtained by mixing and processing NaNbO3 xerogel powder, 80 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder, 200 nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder and an additive to obtain a mixed powder; the green body is made from the mixed powder and then calcined to obtain a relaxor ferroelectric bulk material with both high energy storage density and high energy storage efficiency; the mass ratio of the NaNbO3 xerogel powder, the two Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powders with different particle sizes and the additive is 0.06 - 0.10:1:1; the additive is at least one of BiFeO3, Na 0.5 Bi 0.5 TiO3 or (BiFeO3) 0.5 (Na 0.5 Bi 0.5 TiO3) 0.5 among them.

12. The material according to claim 11, characterized in that, The NaNbO3 xerogel powder, 80nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 O3@NaNbO3 powder, 200nm Ba 0.7 Sr 0.3 Zr 0.2 Ti 0.8 The mass ratio of O3@NaNbO3 powder and the additive is 0.06 - 0.10:1:1:

1.

13. The material according to claim 12, characterized in that, The additive is BiFeO3 and Na 0.5 Bi 0.5 TiO3, and the mass ratio is 1:

1.

14. The material according to claim 11 or 12 or 13, characterized in that, The relative density of the material is 0.96 - 0.98, and the grain size is 190 - 233 nm; The charge storage density of the material is 1.91 - 3.22 J / cm 3 , and the discharge storage density is 1.69 - 3.17 J / cm 3 , and the storage efficiency is 81.8 - 98.4%.

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