A-site doped lead-free ceramic material, method of preparation and use thereof

Abstract

This invention discloses an A-site doped lead-free ceramic material, its preparation method, and its applications, relating to the field of dielectric ceramics technology. This invention simultaneously introduces multiple cations such as Sr, Ca, Bi, and Na into the A-site (Ba) of a barium titanate (BaTiO3) matrix to construct a high-entropy doped structure, effectively controlling lattice distortion and local polarization behavior, thereby obtaining excellent relaxor ferroelectric properties and high breakdown field strength. The material is prepared using an electrospinning combined with heat treatment process to form a nanofiber structure with a beaded morphology, significantly inhibiting abnormal grain growth, increasing density, and reducing defect concentration. The resulting ceramic exhibits high energy density, high energy storage efficiency, and excellent cycle stability over a wide temperature range. It is also free of toxic elements such as lead, making it environmentally friendly and suitable for high-temperature, high-power electronic devices in new energy vehicles, 5G communications, aerospace, and other fields, providing a reliable technical solution for developing next-generation high-performance lead-free energy storage capacitors.

Description

Technical Field

[0001] This invention relates to the field of dielectric ceramics technology, and in particular to an A-site doped lead-free ceramic material, its preparation method, and its application. Background Technology

[0002] With the rapid development of 5G communication, new energy vehicles, aerospace and other fields, electronic devices have an increasingly urgent need for high-temperature stability and high energy density of dielectric energy storage materials. The performance of these materials directly affects the reliability and application expansion of products in related fields. Therefore, the development of high-performance dielectric energy storage materials has become an important direction for industry development.

[0003] Traditional lead-based ceramics (such as Pb(Zr,Ti)O3), while possessing excellent dielectric properties and meeting energy storage requirements to some extent, have a lead content exceeding 60%, easily causing severe environmental pollution throughout production, use, and disposal. While existing lead-free ceramics (such as BaTiO3-based and (K,Na)NbO3-based) solve the environmental problem, they suffer from several unavoidable drawbacks. Regarding structural stability, single-element doping easily leads to lattice distortion, forming second phases such as BaCO3 and SrCO3, directly reducing the breakdown field strength and affecting safety. In terms of high-temperature performance, these materials experience dielectric constant decay exceeding 30% at 300℃, and energy storage efficiency drops below 70%, completely failing to meet the application requirements of high-temperature scenarios. Regarding manufacturing processes, conventional solid-state sintering methods have significant limitations. Ceramic grains prepared using this process are uneven in size, typically in the 5-10 μm range, and have numerous grain boundary defects, directly causing excessive leakage current loss, further affecting the material's energy storage performance and stability.

[0004] The shortcomings of the existing technologies have created an urgent market demand for dielectric materials that combine lead-free environmental friendliness, high energy storage, and wide temperature stability. Developing such materials is key to overcoming the current technological bottlenecks. Summary of the Invention

[0005] The purpose of this invention is to provide an A-site doped lead-free ceramic material, its preparation method, and its applications, thereby addressing the problems existing in the prior art. This invention proposes a technical solution combining A-site multi-element synergistic doping (high entropy effect) with electrospinning, achieving synergistic optimization of the material's microstructure and macroscopic properties, and providing a feasible path to meet the high-end demands of the industry.

[0006] To achieve the above objectives, the present invention provides the following solution: This invention provides an A-site doped lead-free ceramic material with the chemical formula Ba. 1-α-β-n-p Sr α Bi β Can Na p TiO3; wherein, 0.05≤α≤0.3, 0.05≤β≤0.3, 0.05≤n≤0.3, 0.05≤p≤0.3, and α+β+n+p<1 must be satisfied; If the proportion of a certain doping element is >0.3, it will introduce impurity phases such as SrCO3 and Bi2O3, resulting in excessive lattice distortion and reduced breakdown field strength. If the proportion of a certain doping element is <0.05, the high entropy effect of multi-element synergy is not obvious, and it is impossible to effectively control lattice distortion and local polarization.

[0007] This invention also provides a method for preparing the above-mentioned A-site doped lead-free ceramic material, comprising the following steps: (1) Electrospinning: Barium source, strontium source, bismuth source, calcium source, sodium source and titanium source are dissolved in an organic solvent according to the target stoichiometric ratio, spinning aid is added, stirring is performed to form a spinning solution, and electrospinning is carried out to obtain nanofibers; (2) Calcination: The nanofibers are pre-calcined and then calcined to obtain ceramic nanofibers; In this invention, after calcination, the diameter of the obtained ceramic nanofibers is 100~300nm, the diameter of the beaded structure is 500~800nm, the spacing between the beads is 1~3μm, and the proportion of the beaded structure is ≥80%.

[0008] (3) Sintering: The ceramic nanofibers are pressed into shape and sintered at 1150~1250℃ for 50~70min to obtain the A-site doped lead-free ceramic material.

[0009] The A-site doped lead-free ceramic material obtained by this invention has a single-phase perovskite structure (space group Pm-3m), a dielectric constant εr ≥ 4000 at room temperature and 1000 Hz, a dielectric loss tanδ ≤ 0.16, and an energy retention rate ≥ 85% at 300℃.

[0010] As a further preferred embodiment of the present invention, the spinning aid is polyvinylpyrrolidone, and the amount added is 5 to 15 wt% of the total mass of the barium source, strontium source, calcium source, bismuth source, sodium source and titanium source.

[0011] As a further preferred embodiment of the present invention, the molecular weight of polyvinylpyrrolidone is 1,300,000.

[0012] As a further preferred embodiment of the present invention, the barium source includes barium acetate, the strontium source includes strontium acetate, the calcium source includes calcium acetate, the bismuth source includes bismuth acetate, the sodium source includes sodium acetate, and the titanium source includes tetrabutyl titanate.

[0013] As a further preferred embodiment of the present invention, in step (2), the calcination treatment is carried out at a temperature of 700-1100℃ for 2-4 hours.

[0014] As a further preferred embodiment of the present invention, in step (2), the temperature of the pre-firing treatment is 200-300℃ and the time is 20-40min.

[0015] As a further preferred embodiment of the present invention, in step (2), the heating rate of the calcination treatment is 5-10℃ / min, and the temperature is maintained for 30min for every 100℃ increase.

[0016] As a further preferred embodiment of the present invention, in step (1), the organic solvent is a mixed solvent of N,N-dimethylformamide and glacial acetic acid in a volume ratio of 1:1.

[0017] As a further preferred embodiment of the present invention, in step (3), the heating rate of the sintering is 3~5℃ / min.

[0018] As a further preferred embodiment of the present invention, the pressure of the compression molding is 15~25MPa.

[0019] As a further preferred embodiment of the present invention, the parameters of the electrospinning are: voltage 10~20kV, injection rate 0.3~0.8mL / h, distance between needle and receiver 12~18cm, and ambient humidity 30~50%.

[0020] As a further preferred embodiment of the present invention, the pressing is performed by holding the pressure at 15-25 MPa for 3-7 minutes to form a disc blank with a diameter of 10-15 mm and a thickness of 0.5-1 mm.

[0021] As a further preferred embodiment of the present invention, a pre-sintering step is included before sintering to remove the molding aids.

[0022] The present invention further provides the application of the above-mentioned A-site doped lead-free ceramic material as an electronic device.

[0023] Using the A-site doped lead-free ceramic material of this invention as a high-temperature energy storage capacitor material can achieve an operating temperature range of -50~300℃, a charge / discharge efficiency of ≥85%, and a cycle life of ≥10. 5 (1 kHz, 700 kV / cm)

[0024] This invention leverages the high-entropy effect through multi-element synergistic doping at the A-site, laying the structural foundation for material properties. Ba is synergistically introduced at the A-site of the perovskite (ABO3) lattice. 2+ 、Sr 2+ Bi 3+ Ca 2+ Na + Five cations, each ion occupying the A site uniformly in a precise molar ratio, utilizing different ionic radii (Ba...2+ 135pm, Sr 2+ 118pm, Bi 3+ 117pm, Ca 2+ 100pm, Na + The synergistic adaptability of Bi (102pm) effectively suppresses lattice distortion easily induced by single-element doping, while stabilizing the single perovskite structure (space group Pm-3m) through the high-entropy effect, avoiding the formation of second phases such as BaCO3 and SrCO3, and significantly improving the integrity of the lattice structure; among which Bi 3+ The 6s² inert electron pair property of Ca can induce relaxor ferroelectric behavior in materials, broadening the phase transition temperature range and ensuring high-temperature stability. 2+ with Na + Due to its small radius, it can fill the interstices of the crystal lattice and reduce the concentration of oxygen vacancies, thereby reducing leakage current loss and creating conditions for improving the breakdown field strength.

[0025] The beaded nanofiber structure constructed by the electrospinning process of this invention further optimizes dielectric energy storage performance by enhancing interfacial polarization. The spinning solution is subjected to high-voltage electrostatic action to form continuous fibers. The collected precursor fiber mat retains its beaded microstructure after calcination. This structure not only increases the specific surface area of ​​the material but also constructs abundant fiber-bead interfaces, providing sufficient sites for interfacial polarization. Simultaneously, the reasonable size design of the bead structure (bead diameter 500~800nm, bead spacing 1~3μm, accounting for ≥80%) avoids local electric field concentration, disperses electric field stress, and, combined with a uniform element distribution, further enhances the breakdown field strength of the material.

[0026] In the calcination process of this invention, low-temperature sintering is first used to remove spinning aids to avoid the rapid decomposition of organic matter at high temperatures, which would cause the fiber structure to collapse. Then, calcination is carried out at 700-1100℃ and held at that temperature to ensure the grain growth effect and reduce grain boundary defects.

[0027] The present invention discloses the following technical effects: This invention provides an A-site doped lead-free ceramic material, which effectively solves the key technical problems of existing lead-free energy storage ceramics, such as rapid energy storage performance decay, low energy storage efficiency, and poor cycle stability under high temperature conditions.

[0028] This invention significantly optimizes the dielectric response characteristics and breakdown strength of the material through a rational multi-cation co-doping design and unique nanofiber structure regulation, enabling it to maintain excellent energy storage capacity over a wide temperature range. The electrospinning combined with segmented heat treatment process not only effectively suppresses excessive grain growth and achieves uniform and dense microstructure, but also significantly reduces internal defects and leakage current, thereby significantly improving the overall electrical performance and long-term operational reliability, providing a solid structural foundation for high-efficiency energy storage and release.

[0029] Furthermore, the material of this invention is completely free of toxic elements such as lead, which aligns with the development direction of green electronic devices and has broad prospects in high-end application fields such as new energy vehicles, 5G communications, and aerospace, where high-temperature stability and environmental friendliness are stringent requirements.

[0030] In summary, this invention achieves a synergistic breakthrough in energy storage performance and thermal stability of lead-free ceramics while taking into account environmental protection attributes, providing a practical and feasible technical path for the research and development of next-generation high-temperature, high-power capacitors. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a flowchart illustrating the preparation process of A-site doped lead-free ceramic nanofibers according to the present invention.

[0033] Figure 2 The images show the X-ray diffraction (XRD) and Rietveld refinement images of the BSBCNT ceramic nanofibers prepared in Example 1 of this invention.

[0034] Figure 3 The XPS full spectrum of the BSBCNT ceramic nanofibers prepared in Example 1 of this invention is shown.

[0035] Figure 4 This is a scanning electron microscope (SEM) image of the BSBCNT ceramic nanofibers prepared in Example 1 of this invention.

[0036] Figure 5 This is an HR-TEM image of the BSBCNT ceramic nanofibers prepared in Example 1 of the present invention under bright field.

[0037] Figure 6 The temperature-varying dielectric loss diagram (1kHz) of the A-site doped lead-free ceramic materials prepared in Examples 1-5 of this invention is shown.

[0038] Figure 7 The diagram shows the PE ring diagram of the A-site doped lead-free ceramic materials prepared in Examples 1-5 of this invention as a function of electric field strength.

[0039] Figure 8 The temperature-varying dielectric loss diagram (1kHz) of the A-site doped lead-free ceramic material prepared in Examples 6-7 of this invention is shown.

[0040] Figure 9 The PE ring diagram shows the variation of the A-site doped lead-free ceramic material prepared in Examples 6-7 of this invention with electric field strength.

[0041] Figure 10 The temperature-varying dielectric loss diagram (1kHz) of the ceramic materials prepared in Comparative Examples 1-4 of this invention is shown.

[0042] Figure 11 The diagram shows the PE ring diagram of the ceramic materials prepared in Comparative Examples 1-4 of this invention as a function of electric field strength. Detailed Implementation

[0043] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0044] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0045] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0046] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0047] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0048] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0049] In the following embodiments of the present invention, the purity of barium acetate, strontium acetate, calcium acetate, bismuth acetate, sodium acetate and tetrabutyl titanate is ≥98.0%; the purity of N,N-dimethylformamide and glacial acetic acid is ≥99.0%.

[0050] In the following embodiments of the present invention, the molecular weight of polyvinylpyrrolidone used is 1,300,000.

[0051] In the following embodiments of the present invention, the formula for calculating the energy retention rate is as follows: Energy retention rate (%) = (energy storage density at 300℃ / energy storage density at room temperature) × 100%.

[0052] Example 1 This embodiment provides a method for preparing A-site doped lead-free ceramic materials, the steps of which are as follows: (1) Preparation of spinning solution: According to the molar ratio Ba(CH3COO)2:Sr(CH3COO)2:Bi(CH3COO)3:Ca(CH3COO)2:NaCH3COO:Ti(C 16 H 36 Accurately weigh each raw material according to the formula (O4) = 0.2:0.2:0.2:0.2:0.2:1. Add the raw materials to the mixed solvent at a mass-to-volume ratio of 1:5 (g / mL) (i.e., 1g of raw material corresponds to 5mL of mixed solvent). Then add the raw materials to the mixed solvent of N,N-dimethylformamide and glacial acetic acid in a volume ratio of 1:1. Add 10wt% of polyvinylpyrrolidone according to the total mass of the raw materials. Stir magnetically at 300rpm for 3h to obtain the spinning solution (viscosity 3500cP).

[0053] (2) Electrospinning: Inject the spinning solution into a 10mL syringe (needle inner diameter 0.6mm), set the electrospinning parameters as follows: voltage 15kV, injection rate 0.5mL / h, distance between needle and receiver 15cm, roller (coated with aluminum foil) speed 80rpm, ambient temperature 25℃, ambient humidity 40%, start the equipment to spin, and collect for 2h to obtain a fiber mat (precursor) with a thickness of 0.5mm.

[0054] (3) Calcination treatment: The collected fiber felt was placed in an alumina crucible and calcined in a muffle furnace in stages: the temperature was increased from room temperature to 250℃ at a heating rate of 5℃ / min, and held at 250℃ for 30min to remove polyvinylpyrrolidone; then the temperature was increased at a heating rate of 8℃ / min, and held for 30min every 100℃ increase. After the holding period, the temperature was increased again until it reached 1100℃ and then the heating was stopped; after cooling in the furnace, BSBCNT ceramic nanofibers (labeled as BSBCNT11 ceramic nanofibers) were obtained. The obtained BSBCNT ceramic nanofibers had a diameter of 200nm, a beaded structure morphology with a diameter of 100~300nm, a bead diameter of 500~800nm, a bead spacing of 1~3μm, and a beaded structure accounting for 85%.

[0055] (4) Pressing and sintering: BSBCNT11 ceramic nanofibers and 6wt% polyvinyl alcohol aqueous solution were mixed and granulated. The mass ratio of BSBCNT11 ceramic nanofibers to polyvinyl alcohol aqueous solution was 10:1. The mixture was pressed into shape (diameter 12mm, thickness 0.8mm) under 20MPa pressure for 5 minutes. The shaped blank was then pre-fired and sintered. That is, it was pre-fired at 200℃ for 2 hours, and then heated to 1200℃ at a heating rate of 3℃ / min for 60 minutes. The blank was then polished with sandpaper to Ra=0.3μm to complete the preparation of ceramic samples.

[0056] Figure 2 The images show the X-ray diffraction (XRD) and Rietveld refinement patterns of BSBCNT11 ceramic nanofibers. The characteristic peaks of the XRD pattern (2θ = 22.1°, 31.5°, 38.8°, 45.2°, 50.9°) perfectly match the standard card (PDF#05-0626) for perovskite-type BaTiO3, and there are no characteristic peaks of impurity phases such as SrCO3 and Bi2O3. The Rietveld refinement has verified that its crystal space group is Pm-3m and its crystallinity is ≥95%, confirming it as a single-phase perovskite structure.

[0057] Figure 3 This is the XPS full spectrum of the BSBCNT ceramic nanofibers prepared in Example 1 of this invention. The full spectrum of the sample sintered at 1100℃ is shown, clearly displaying the characteristic peaks of Ba, Sr, Bi, Ca, Na, Ti, and O, indicating that all target elements were successfully introduced without impurities.

[0058] Figure 4This is a scanning electron microscope (SEM) image of the BSBCNT ceramic nanofibers prepared in Example 1 of this invention. It shows a typical beaded nanofiber morphology with uniform fiber diameter and smooth surface, indicating that the electrospinning process successfully constructed nanofibers with a periodic "bead-wire" structure. This morphology provides more active sites for interfacial polarization and charge storage.

[0059] Figure 5 This is a bright-field HR-TEM image of the BSBCNT ceramic nanofibers prepared in Example 1 of this invention. It reveals randomly distributed nanodomain regions within the ceramic matrix. These nanodomains consist of ordered parallel stripes with a width of approximately 0.29 nm, conforming to moiré fringe characteristics, indicating the presence of localized lattice distortion and stress fields within the material.

[0060] The prepared ceramic samples were subjected to performance testing. The relevant testing standards were GB / T 5594.4-2015 "Test Methods for Performance of Structural Ceramic Materials for Electronic Components Part 4: Test Methods for Dielectric Constant and Dielectric Loss Tangent" and GB / T 3389-2008 "Test Methods for Performance Parameters of Piezoelectric Ceramic Materials".

[0061] The test results are as follows: At room temperature (25℃), the average breakdown field strength of the sample is 623.2 kV / cm, the energy density is 15.0 J / cm³, the energy storage efficiency is 88.62%, the dielectric constant (1 kHz) is 4020, and the dielectric loss (1 kHz) is 0.05; at 200℃, the average breakdown field strength of the sample is 598.5 kV / cm, the energy density is 14.5 J / cm³, the energy storage efficiency is 91.2%, the dielectric constant (1 kHz) is 2678, and the dielectric loss (1 kHz) is 0.03; at 300℃, the average breakdown field strength of the sample is 572.8 kV / cm, the energy density is 14.0 J / cm³, the energy storage efficiency is as high as 92.88%, and the energy retention rate is 93.3%.

[0062] Example 2 This embodiment provides a method for preparing A-site doped lead-free ceramic materials, the steps of which are as follows: (1)-(2) Same as Example 1.

[0063] (3) Calcination treatment: The collected fiber felt was placed in an alumina crucible and calcined in a muffle furnace in stages: the temperature was increased from room temperature to 250°C at a heating rate of 5°C / min, and held at 250°C for 30 min to remove polyvinylpyrrolidone; then the temperature was increased at a heating rate of 8°C / min, and held for 30 min every 100°C increase. After the holding period, the temperature was increased again until it reached 700°C and then the heating was stopped; after cooling in the furnace, BSBCNT ceramic nanofibers (labeled as BSBCNT7 ceramic nanofibers) were obtained.

[0064] (4) Same as Example 1.

[0065] The prepared ceramic samples were subjected to performance testing, and the testing standards were the same as in Example 1.

[0066] The test results are as follows: At room temperature (25℃), the average breakdown field strength of the sample is 488.2 kV / c, the energy density is 14.3 J / cm³, the energy storage efficiency is 82.08%, the dielectric constant (1 kHz) is 3575, and the dielectric loss (1 kHz) is 0.08; at 200℃, the average breakdown field strength of the sample is 462.7 kV / c, the energy density is 12.8 J / cm³, the energy storage efficiency is 86.5%, the dielectric constant (1 kHz) is 2203, and the dielectric loss (1 kHz) is 0.04; at 300℃, the average breakdown field strength of the sample is 438.1 kV / cm, the energy density is 11.4 J / cm³, the energy storage efficiency is 89.73%, and the energy retention rate is 79.7%.

[0067] Example 3 This embodiment provides a method for preparing A-site doped lead-free ceramic materials, the steps of which are as follows: (1) Same as Example 1; (2) Electrospinning: Inject the spinning solution into a 10mL syringe (needle inner diameter 0.6mm), set the electrospinning parameters as follows: voltage 18kV, injection rate 0.6mL / h, distance between needle and receiver 15cm, roller (coated with aluminum foil) speed 80rpm, ambient temperature 25℃, ambient humidity 40%, start the equipment to spin, and collect for 2h to obtain a fiber mat (precursor) with a thickness of 0.5mm.

[0068] (3) Calcination treatment: The collected fiber felt was placed in an alumina crucible and calcined in a muffle furnace in stages: the temperature was increased from room temperature to 250°C at a heating rate of 5°C / min, and held at 250°C for 30 min to remove polyvinylpyrrolidone; then the temperature was increased at a heating rate of 8°C / min, and held for 30 min every 100°C increase. After the holding period, the temperature was increased again until it reached 800°C and then the heating was stopped; after cooling in the furnace, BSBCNT ceramic nanofibers (labeled as BSBCNT8 ceramic nanofibers) were obtained.

[0069] (4) Same as Example 1.

[0070] The prepared ceramic samples were subjected to performance testing, and the testing standards were the same as in Example 1.

[0071] The test results are as follows: At room temperature (25℃), the average breakdown field strength of the sample is 540.2 kV / cm, the energy density is 15.0 J / cm³, the energy storage efficiency is 84.18%, the dielectric constant (1 kHz) is 3657, and the dielectric loss (1 kHz) is 0.06; at 200℃, the average breakdown field strength of the sample is 513.2 kV / cm, the energy density is 13.5 J / cm³, the energy storage efficiency is 85.8%, the dielectric constant (1 kHz) is 2296, and the dielectric loss (1 kHz) is 0.02; at 300℃, the average breakdown field strength of the sample is 487.6 kV / cm, the energy density is 12.1 J / cm³, the energy storage efficiency is 87.6%, and the energy retention rate is 80.6%.

[0072] Example 4 This embodiment provides a method for preparing A-site doped lead-free ceramic materials, the steps of which are as follows: (1) Preparation of spinning solution: According to the molar ratio Ba(CH3COO)2:Sr(CH3COO)2:Bi(CH3COO)3:Ca(CH3COO)2:NaCH3COO:Ti(C 16 H 36 Accurately weigh each raw material according to the formula (O4) = 0.2:0.2:0.2:0.2:0.2:1. Add the raw materials to the mixed solvent at a mass-to-volume ratio of 1:5 (g / mL) (i.e., 1g of raw material corresponds to 5mL of mixed solvent). Then add the raw materials to the mixed solvent of N,N-dimethylformamide and glacial acetic acid in a volume ratio of 1:1. Add 12wt% of polyvinylpyrrolidone according to the total mass of the raw materials. Stir magnetically at 300rpm for 3h to obtain the spinning solution (viscosity 3500cP).

[0073] (2) Same as Example 1.

[0074] (3) Calcination treatment: The collected fiber felt was placed in an alumina crucible and calcined in a muffle furnace in stages: the temperature was increased from room temperature to 250°C at a heating rate of 5°C / min, and held at 250°C for 30 min to remove polyvinylpyrrolidone; then the temperature was increased at a heating rate of 8°C / min, and held at 100°C for 30 min after each increase. After the holding period, the temperature was increased again until it reached 900°C and then the heating was stopped; after cooling in the furnace, BSBCNT ceramic nanofibers (labeled as BSBCNT9 ceramic nanofibers) were obtained.

[0075] (4) Same as Example 1.

[0076] The prepared ceramic samples were subjected to performance testing, and the testing standards were the same as in Example 1.

[0077] The test results are as follows: At room temperature (25℃), the average breakdown field strength of the sample is 559.3 kV / cm, the energy density is 13.8 J / cm³, the energy storage efficiency is 82.14%, the dielectric constant (1 kHz) is 3772, and the dielectric loss (1 kHz) is 0.05; at 200℃, the average breakdown field strength of the sample is 531.3 kV / cm, the energy density is 13.2 J / cm³, the energy storage efficiency is 88.4%, the dielectric constant (1 kHz) is 2450, and the dielectric loss (1 kHz) is 0.02; at 300℃, the average breakdown field strength of the sample is 504.6 kV / cm, the energy density is 12.8 J / cm³, the energy storage efficiency is 89.5%, and the energy retention rate is 92.7%.

[0078] Example 5 This embodiment provides a method for preparing A-site doped lead-free ceramic materials, the steps of which are as follows: (1)-(2) Same as Example 1.

[0079] (3) Calcination treatment: The collected fiber felt was placed in an alumina crucible and calcined in a muffle furnace in stages: the temperature was increased from room temperature to 250℃ at a heating rate of 5℃ / min, and held at 250℃ for 30min to remove polyvinylpyrrolidone; then the temperature was increased at a heating rate of 8℃ / min, and held for 30min for every 100℃ increase. After the holding period, the temperature was increased again until it reached 1000℃ and then the heating was stopped; after natural cooling, BSBCNT ceramic nanofibers (labeled as BSBCNT10 ceramic nanofibers) were obtained.

[0080] (4) Mix BSBCNT10 ceramic nanofibers with 6wt% polyvinyl alcohol aqueous solution and granulate them. The mass ratio of BSBCNT10 ceramic nanofibers to polyvinyl alcohol aqueous solution is 10:1. Press the mixture under 20MPa pressure for 5 minutes to form a 12mm diameter and 0.8mm thickness. Then, pre-fire and sinter the shaped blank. First, pre-fire at 200℃ for 2 hours, then sinter at 1200℃ for 70 minutes at a heating rate of 3℃ / min. Polish the blank with sandpaper to Ra=0.3μm to complete the preparation of the ceramic sample.

[0081] The prepared ceramic samples were subjected to performance testing, and the testing standards were the same as in Example 1.

[0082] The test results are as follows: At room temperature (25℃), the average breakdown field strength of the sample is 582.0 kV / cm, the energy density is 14.7 J / cm³, the energy storage efficiency is 84.53%, the dielectric constant (1 kHz) is 3867, and the dielectric loss (1 kHz) is 0.04; at 200℃, the average breakdown field strength of the sample is 553.7 kV / cm, the energy density is 13.9 J / cm³, the energy storage efficiency is 88.7%, the dielectric constant (1 kHz) is 2545, and the dielectric loss (1 kHz) is 0.02; at 300℃, the average breakdown field strength of the sample is 525.4 kV / cm, the energy density is 13.2 J / cm³, the energy storage efficiency is 90.1%, and the energy retention rate is 89.8%.

[0083] The lead-free ceramic material with A-site doping prepared by this invention has a lead content of <10ppm, which meets the standards of RoHS, GB / T 26572, etc., and can replace traditional lead-based ceramics.

[0084] Figure 6 The temperature-varying dielectric loss diagram (1kHz) of the A-site doped lead-free ceramic materials prepared in Examples 1-5 of this invention shows that the dielectric constant peak of the material exhibits a broadened shape (without sharp phase transition peaks), and the phase transition temperature range is broadened to 100℃~200℃ (the phase transition temperature of traditional barium titanate ceramics is only about 120℃). This conforms to the core characteristics of relaxor ferroelectric materials: "broadened dielectric peak and diffused phase transition temperature," proving that Bi 3+ The 6s² inert electron pair induces relaxor ferroelectric behavior.

[0085] Figure 7 The diagram shows the PE ring diagram of the A-site doped lead-free ceramic materials prepared in Examples 1-5 of this invention as a function of electric field strength.

[0086] Example 6 This embodiment provides a method for preparing A-site doped lead-free ceramic materials, the steps of which are as follows: (1) Preparation of spinning solution: According to the molar ratio Ba(CH3COO)2:Sr(CH3COO)2:Bi(CH3COO)3:Ca(CH3COO)2:NaCH3COO:Ti(C 16 H 36 Accurately weigh each raw material according to the formula (O4) = 0.8:0.05:0.05:0.05:0.05:1. Add the raw materials to the mixed solvent at a mass-to-volume ratio of 1:5 (g / mL) (i.e., 1g of raw material corresponds to 5mL of mixed solvent). Then add the raw materials to the mixed solvent of N,N-dimethylformamide and glacial acetic acid at a volume ratio of 1:1. Add 12wt% of polyvinylpyrrolidone according to the total mass of the raw materials. Stir magnetically at 300rpm for 3h to obtain the spinning solution (viscosity 3500cP).

[0087] (2)-(4) Same as Example 1.

[0088] The prepared ceramic samples were subjected to performance testing, and the testing standards were the same as in Example 1.

[0089] The test results are as follows: At room temperature (25℃), the average breakdown field strength of the sample is 550.0 kV / cm, the energy density is 13.3 J / cm³, the energy storage efficiency is 87.15%, the dielectric constant (1 kHz) is 3772, and the dielectric loss (1 kHz) is 0.15; at 200℃, the average breakdown field strength of the sample is 522.5 kV / cm, the energy density is 12.6 J / cm³, the energy storage efficiency is 88.3%, the dielectric constant (1 kHz) is 2638, and the dielectric loss (1 kHz) is 0.05; at 300℃, the average breakdown field strength of the sample is 495.1 kV / cm, the energy density is 11.8 J / cm³, the energy storage efficiency is 89.5%, and the energy retention rate is 88.7%.

[0090] Example 7 This embodiment provides a method for preparing A-site doped lead-free ceramic materials, the steps of which are as follows: (1) Preparation of spinning solution: According to the molar ratio Ba(CH3COO)2:Sr(CH3COO)2:Bi(CH3COO)3:Ca(CH3COO)2:NaCH3COO:Ti(C 16 H 36Accurately weigh each raw material according to the formula (O4) = 0.15:0.25:0.2:0.2:0.2:1. Add the raw materials to the mixed solvent at a mass-to-volume ratio of 1:5 (g / mL) (i.e., 1g of raw material corresponds to 5mL of mixed solvent). Then add the raw materials to the mixed solvent of N,N-dimethylformamide and glacial acetic acid at a volume ratio of 1:1. Add 12wt% of polyvinylpyrrolidone according to the total mass of the raw materials. Stir magnetically at 300rpm for 3h to obtain the spinning solution (viscosity 3500cP).

[0091] (2)-(4) Same as Example 1.

[0092] The prepared ceramic samples were subjected to performance testing, and the testing standards were the same as in Example 1.

[0093] The test results are as follows: At room temperature (25℃), the average breakdown field strength of the sample is 590.3 kV / cm, the energy density is 13.8 J / cm³, the energy storage efficiency is 89.46%, the dielectric constant (1 kHz) is 3972, and the dielectric loss (1 kHz) is 0.12; at 200℃, the average breakdown field strength of the sample is 560.8 kV / cm, the energy density is 13.0 J / cm³, the energy storage efficiency is 89.2%, the dielectric constant (1 kHz) is 2548, and the dielectric loss (1 kHz) is 0.03; at 300℃, the average breakdown field strength of the sample is 531.7 kV / cm, and the energy density is 12.3 J / cm³. 3 The energy storage efficiency is 88.5%, and the energy retention rate is 89.1%.

[0094] Figure 8 The temperature-varying dielectric loss diagram (1kHz) of the A-site doped lead-free ceramic material prepared in Examples 6-7 of this invention is shown.

[0095] Figure 9 The PE ring diagram shows the variation of the A-site doped lead-free ceramic material prepared in Examples 6-7 of this invention with electric field strength.

[0096] Comparative Example 1 This embodiment provides a method for preparing A-site doped lead-free ceramic materials, the steps of which are as follows: (1) Preparation of spinning solution: According to the molar ratio Ba(CH3COO)3:Sr(CH3COO)2:La(CH3COO)3:Ca(CH3COO)2:NaCH3COO:Ti(C 16 H 36Accurately weigh each raw material according to the formula (O4) = 0.2:0.2:0.2:0.2:0.2:1, and add it to the mixed solvent at a mass-to-volume ratio of 1:5 (g / mL) (i.e., 1g of raw material corresponds to 5mL of mixed solvent). Then add the raw materials to the mixed solvent of N,N-dimethylformamide and glacial acetic acid in a volume ratio of 1:1, and then add 10wt% of polyvinylpyrrolidone according to the total mass of the raw materials. Stir magnetically at 300rpm for 3h to obtain the spinning solution (viscosity 3500cP).

[0097] (2) Same as Example 1.

[0098] (3) Calcination treatment: The collected fiber felt was placed in an alumina crucible and calcined in a muffle furnace in stages: the temperature was increased from room temperature to 250°C at a heating rate of 5°C / min, and held at 250°C for 30 min to remove polyvinylpyrrolidone; then the temperature was increased at a heating rate of 8°C / min, and held for 30 min every 100°C increase. After the holding period, the temperature was increased again until it reached 1100°C and then the heating was stopped; after cooling in the furnace, BSLCNT ceramic nanofibers (labeled as BSLCNT11 ceramic nanofibers) were obtained.

[0099] (4) Same as Example 1.

[0100] The prepared ceramic samples were subjected to performance testing, and the testing standards were the same as in Example 1.

[0101] The test results are as follows: At room temperature (25℃), the average breakdown field strength of the sample is 552.7 kV / cm, the energy density is 9.5 J / cm³, the energy storage efficiency is 70.2%, the dielectric constant (1 kHz) is 2875, and the dielectric loss (1 kHz) is 0.11; at 200℃, the average breakdown field strength of the sample is 525.1 kV / cm, the energy density is 8.3 J / cm³, the energy storage efficiency is 69.5%, the dielectric constant (1 kHz) is 1504, and the dielectric loss (1 kHz) is 0.03; at 300℃, the average breakdown field strength of the sample is 497.6 kV / cm, the energy density is 7.2 J / cm³, the energy storage efficiency is 68.1%, and the energy retention rate is 75.8%.

[0102] Comparative Example 2 This embodiment provides a method for preparing A-site doped lead-free ceramic materials, the steps of which are as follows: (1) Preparation of spinning solution: According to the molar ratio Ba(CH3COO)2:Sr(CH3COO)2:Bi(CH3COO)3:Ca(CH3COO)2:NaCH3COO:Ti(C 16 H 36Accurately weigh each raw material according to the formula (O4) = 0.2:0.2:0.2:0.2:0.2:1, and add it to the mixed solvent at a mass-to-volume ratio of 1:5 (g / mL) (i.e., 1g of raw material corresponds to 5mL of mixed solvent). Then add the raw materials to the mixed solvent of N,N-dimethylformamide and glacial acetic acid in a volume ratio of 1:1, and then add 10wt% of polyvinylpyrrolidone according to the total mass of the raw materials. Stir magnetically at 300rpm for 3h to obtain a sol.

[0103] (2) The sol was dried in an oven at 60°C for 24 hours to obtain a dry gel, which was then ground into powder.

[0104] (3) Calcination treatment: The collected powder was placed in an alumina crucible and calcined in a muffle furnace in stages: the temperature was increased from room temperature to 250°C at a heating rate of 5°C / min, and held at 250°C for 30 min to remove polyvinylpyrrolidone; then the temperature was increased at a heating rate of 8°C / min, and held for 30 min every 100°C increase. After the holding period, the temperature was increased again until it reached 1100°C and then the heating was stopped; after cooling in the furnace, BSBCNT ceramic powder was obtained.

[0105] (4) Same as Example 1.

[0106] Because the "electric field stretching and fiber formation" effect of electrospinning was not used, the powder after dry gel grinding was only an irregular nanoparticle aggregate (particle size distribution 200~500nm), without any beaded structure morphology, and could not form the continuous beaded nanofibers in Example 1.

[0107] The prepared ceramic samples were subjected to performance testing, and the testing standards were the same as in Example 1.

[0108] The test results are as follows: At room temperature (25℃), the average breakdown field strength of the sample is 465.0 kV / cm, the energy density is 8.8 J / cm³, the energy storage efficiency is 65.1%, the dielectric constant (1 kHz) is 2757, and the dielectric loss (1 kHz) is 0.14; at 200℃, the average breakdown field strength of the sample is 438.2 kV / cm, the energy density is 7.5 J / cm³, the energy storage efficiency is 62.3%, the dielectric constant (1 kHz) is 1395, and the dielectric loss (1 kHz) is 0.04; at 300℃, the average breakdown field strength of the sample is 411.5 kV / cm, the energy density is 6.3 J / cm³, the energy storage efficiency is 58.20%, and the energy retention rate is 71.6%.

[0109] Comparative Example 3 This embodiment provides a method for preparing A-site doped lead-free ceramic materials, the steps of which are as follows: (1) Preparation of spinning solution: According to the molar ratio Ba(CH3COO)2:Sr(CH3COO)2:Bi(CH3COO)3:Ca(CH3COO)2:NaCH3COO:Ti(C 16 H 36 Accurately weigh each raw material (only the Sr proportion α=0.35>0.3, the proportions of other elements remain unchanged, and the Ba proportion is adjusted to 1-0.35-0.2-0.2-0.2=0.05, satisfying α+β+n+p=0.95<1). The mass-to-volume ratio of the total raw material mass to the mixed solvent is 1:5 (g / mL) (i.e., 1g of total raw material mass corresponds to 5mL of mixed solvent). Then, add the raw material to the mixed solvent of N,N-dimethylformamide and glacial acetic acid in a volume ratio of 1:1, and then add 10wt% of polyvinylpyrrolidone according to the total raw material mass. Stir magnetically at 300rpm for 3h to obtain the spinning solution (viscosity 3500cP).

[0110] (2) Same as Example 1.

[0111] (3) Same as Example 1.

[0112] (4) Same as Example 1.

[0113] When the Sr content is >0.3%, the SrCO3 impurity phase is introduced, resulting in excessive lattice distortion and a significant decrease in breakdown field strength, energy storage performance, and high-temperature stability. The prepared ceramic samples were subjected to performance testing using the same standards as in Example 1.

[0114] The test results are as follows: At room temperature (25℃), the average breakdown field strength of the sample is 425.6 kV / cm, the energy density is 10.2 J / cm³, the energy storage efficiency is 75.2%, the dielectric constant (1 kHz) is 2850, and the dielectric loss (1 kHz) is 0.21; at 200℃, the average breakdown field strength of the sample is 404.3 kV / cm, the energy density is 8.9 J / cm³, the energy storage efficiency is 71.4%, the dielectric constant (1 kHz) is 1920, and the dielectric loss (1 kHz) is 0.08; at 300℃, the average breakdown field strength of the sample is 383.1 kV / cm, the energy density is 7.4 J / cm³, the energy storage efficiency is 68.3%, and the energy retention rate is 72.5%.

[0115] Comparative Example 4 This embodiment provides a method for preparing A-site doped lead-free ceramic materials, the steps of which are as follows: (1) Preparation of spinning solution: According to the molar ratio Ba(CH3COO)2:Sr(CH3COO)2:Bi(CH3COO)3:Ca(CH3COO)2:NaCH3COO:Ti(C16 H 36 The following raw materials were accurately weighed (O4) = 0.37:0.2:0.03:0.2:0.2:1 (only the proportion of Bi is β=0.03<0.05, the proportions of other elements remain unchanged, and the proportion of Ba is adjusted to 1-0.2-0.03-0.2-0.2=0.37, satisfying α+β+n+p=0.63<1). The mass-to-volume ratio of the total raw material mass to the mixed solvent was 1:5 (g / mL) (i.e., 1g of the total raw material mass corresponds to 5mL of the mixed solvent). The raw materials were then added to a mixed solvent of N,N-dimethylformamide and glacial acetic acid in a volume ratio of 1:1. Polyvinylpyrrolidone was then added, accounting for 10wt% of the total raw material mass. The mixture was magnetically stirred at 300rpm for 3h to obtain the spinning solution (viscosity 3500cP).

[0116] (2) Same as Example 1.

[0117] (3) Same as Example 1.

[0118] (4) Same as Example 1.

[0119] When the Bi content is <0.05%, the multi-element synergistic high-entropy effect is not obvious, and it is impossible to effectively control lattice distortion and local polarization, resulting in a significant decrease in polarization intensity, breakdown field strength, and high-temperature energy storage performance. The prepared ceramic samples were tested according to the same standards as in Example 1.

[0120] The test results are as follows: At room temperature (25℃), the average breakdown field strength of the sample is 510.8 kV / cm, the energy density is 11.3 J / cm³, the energy storage efficiency is 80.5%, the dielectric constant (1 kHz) is 3200, and the dielectric loss (1 kHz) is 0.10; at 200℃, the average breakdown field strength of the sample is 485.3 kV / cm, the energy density is 9.8 J / cm³, the energy storage efficiency is 79.2%, the dielectric constant (1 kHz) is 2050, and the dielectric loss (1 kHz) is 0.04; at 300℃, the average breakdown field strength of the sample is 459.7 kV / cm, the energy density is 8.9 J / cm³, the energy storage efficiency is 78.2%, and the energy retention rate is 78.8%.

[0121] Figure 10 The temperature-varying dielectric loss diagram (1kHz) of the ceramic materials prepared in Comparative Examples 1-4 of this invention is shown.

[0122] Figure 11 The diagram shows the PE ring diagram of the ceramic materials prepared in Comparative Examples 1-4 of this invention as a function of electric field strength.

[0123] Effect verification example The effectiveness of the material of this invention in high-temperature energy storage capacitors is verified as follows: (1) Device structure and composition: The fabricated high-temperature energy storage capacitor adopts a stacked structure of "aluminum electrode-ceramic dielectric layer-aluminum electrode", and the specific parameters are as follows: Ceramic dielectric layer: The A-site doped lead-free ceramic material of the present invention is used, with a thickness of 100 μm and an overall size of 20 mm × 20 mm; Electrode: An aluminum electrode prepared by magnetron sputtering with a thickness of 200 nm and an effective electrode area of ​​15 mm × 15 mm; Packaging: Polyimide film is used for packaging to ensure that the device can operate stably over a wide temperature range of -50 ℃ to 300 ℃.

[0124] (2) Device fabrication steps The A-site doped lead-free ceramic material prepared in Example 1 of this invention (BSBCNT11) was ground, pressed (pressure 20 MPa, holding pressure for 5 min), sintered (holding temperature at 1200 ℃ for 60 min), and then polished to a thickness of 100 μm to obtain a dense and uniform ceramic dielectric sheet. Subsequently, aluminum electrodes were deposited on both sides of the sheet using a magnetron sputtering instrument. Finally, the entire device was encapsulated with a polyimide film to complete the fabrication of the high-temperature energy storage capacitor.

[0125] (3) Performance verification results Under test conditions of 1 kHz frequency and 550 kV / cm electric field strength, this capacitor exhibits excellent overall performance. Its operating temperature range covers -50℃ to 300℃, and it operates stably throughout the entire temperature range; the charge / discharge efficiency is 88.2% at -50℃, 89.5% at 0℃, and reaches 90.5% at room temperature (25℃), maintaining 86.1% even at a high temperature of 300℃, with an efficiency of no less than 85% across the entire temperature range. Furthermore, after continuous testing for 10... 5 After several charge-discharge cycles, the charge-discharge efficiency retention rates (post-cycle efficiency / initial efficiency × 100%) at various temperatures were as follows: 90.2% at -50℃, 93.5% at 0℃, 92.3% at room temperature (25℃), and 88.5% at 300℃. The cycle efficiency retention rate at all temperatures was no less than 88%, fully demonstrating its excellent long-term cycle stability and reliability.

[0126] The material of this invention has extremely high practical value in high-temperature energy storage capacitors, and has significant technical advantages in terms of wide temperature stability and long cycle life.

[0127] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A lead-free ceramic material doped at the A-site, characterized in that, The chemical formula is Ba 1-α-β-n-p Sr α Bi β Ca n Na p TiO3; wherein, 0.05≤α≤0.3, 0.05≤β≤0.3, 0.05≤n≤0.3, 0.05≤p≤0.3, and satisfy α+β+n+p<1.

2. The method for preparing A-site doped lead-free ceramic material as described in claim 1, characterized in that, Includes the following steps: (1) Electrospinning: Barium source, strontium source, bismuth source, calcium source, sodium source and titanium source are dissolved in an organic solvent according to the target stoichiometric ratio, spinning aid is added, stirring is performed to form a spinning solution, and electrospinning is carried out to obtain nanofibers; (2) Calcination: The nanofibers are pre-calcined and then calcined to obtain ceramic nanofibers; (3) Sintering: The ceramic nanofibers are pressed into shape and sintered at 1150~1250℃ for 50~70min to obtain the A-site doped lead-free ceramic material.

3. The preparation method according to claim 2, characterized in that, The barium source includes barium acetate, the strontium source includes strontium acetate, the calcium source includes calcium acetate, the bismuth source includes bismuth acetate, the sodium source includes sodium acetate, and the titanium source includes tetrabutyl titanate.

4. The preparation method according to claim 2, characterized in that, In step (2), the calcination treatment is carried out at a temperature of 700-1100℃ for 2-4 hours.

5. The preparation method according to claim 4, characterized in that, In step (2), the pre-burning treatment is carried out at a temperature of 200-300℃ for 20-40 minutes.

6. The preparation method according to claim 4, characterized in that, In step (2), the heating rate of the calcination treatment is 5-10℃ / min, and the temperature is maintained for 30min for every 100℃ increase.

7. The preparation method according to claim 2, characterized in that, In step (1), the organic solvent is a mixture of N,N-dimethylformamide and glacial acetic acid in a volume ratio of 1:

1.

8. The preparation method according to claim 2, characterized in that, In step (3), the heating rate of the sintering is 3~5℃ / min.

9. The preparation method according to claim 2, characterized in that, The pressure for compression molding is 15~25MPa.

10. The application of the A-site doped lead-free ceramic material as described in claim 1 as an electronic device.

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