Perovskite structure two-phase composite ferroelectric ceramic material with excellent dielectric energy storage and preparation method of perovskite structure two-phase composite ferroelectric ceramic material

Abstract

The invention provides a perovskite structure two-phase composite ferroelectric ceramic material with excellent dielectric energy storage and a preparation method thereof, and relates to the field of relaxor ferroelectric ceramic dielectric energy storage materials. The chemical formula of the ceramic material is (0.6-x) Bi < 0.5 > Na < 0.5 > TiO < 3-0.4 > BaTiO < 3-x > CaZrO < 3 >, x is greater than or equal to 0.1 and less than or equal to 0.2, and when x is in the interval, two perovskite phases are compounded. The relaxor ferroelectric ceramic disclosed by the invention has high breakdown field strength and high polarization intensity. Under the electric field of 115 MV / m, the energy storage density can reach 30.7 J / cm < 3 >, the energy storage efficiency can reach 85%, and the excellent effect is achieved.

Description

Technical Field

[0001] The present invention relates to the field of relaxor ferroelectric ceramic dielectric energy storage materials, and in particular to a perovskite structure two-phase composite ferroelectric ceramic material with excellent dielectric energy storage and a preparation method thereof. Background Art

[0002] As a secondary energy source, electricity occupies a dominant position in daily life and industrial production due to its affordability, versatility, and ease of transportation. Compared to traditional fossil fuels, electricity generated from renewable resources can effectively reduce resource depletion and environmental pollution. However, due to its intermittent, volatile, and random nature, its practicality and expected demand vary in time and space, seriously hindering its large-scale development and application. There is an urgent need to develop advanced technologies to address the storage and conversion of electrical energy.

[0003] Currently, research in energy storage technologies focuses on dielectric capacitors, electrochemical capacitors, and batteries. Dielectric capacitors can store electrical energy as electrostatic fields, offering ultrafast charge and discharge rates, high power density, and long lifespans. They are integral to high-pulse power technologies, including electrified transportation and advanced propulsion. Despite this, the low energy storage density of dielectric ceramic capacitors relative to electrochemical energy storage systems has inhibited their wider adoption. This constraint becomes particularly challenging when striving for high energy capacitance. Consequently, there is an increasing demand to increase their energy density, with the goal of developing cutting-edge integrated and miniaturized applications. Dielectric materials with large maximum polarization, low hysteresis, and high breakdown strength are generally ideal for achieving high energy storage performance. Relaxor ferroelectric ceramics, due to their strong polarizability and low dielectric constant, have been widely used in dielectric energy storage. Summary of the Invention

[0004] The technical problem to be solved by the present invention is that relaxor ferroelectric ceramics have low breakdown field strength, low energy storage density, and low efficiency under high electric fields. Therefore, a perovskite structure two-phase composite ferroelectric ceramic material with excellent dielectric energy storage and a preparation method thereof are provided. The present invention generates fine perovskite two-phase composite relaxor ceramics through a spinodal decomposition strategy and achieves high energy storage performance. Spinodal decomposition stands out as a spontaneous process, in which a single homogeneous phase diffuses uphill and separates without nucleation into two coexisting phases with the same crystal structure but different chemical composition. Several elements with large differences in ionic radius and suitable content ratios are introduced into the A position of the perovskite structure, such as Ba. 2+ (1.61 Å) and Ca 2+ (1.34 Å), resulting in phase separation and forming a perovskite two-phase composite structure with an appropriate ratio. The results show that the composite structure produced by this strategy effectively improves the breakdown strength and maximum polarization of the ceramic material.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] In the first aspect, a perovskite structure two-phase composite ferroelectric ceramic material with excellent dielectric energy storage is provided, wherein the chemical formula is (0.6-x)Bi 0.5 Na 0.5 TiO3-0.4BaTiO3-xCaZrO3.

[0007] In the present invention, when 0.1≤x≤0.2, the ceramic material has two composite perovskite phases. This is manifested by the XRD spectrum of the perovskite two-phase composite relaxor ferroelectric ceramic material, in which all perovskite characteristic peaks have two diffraction peaks. This indicates that the perovskite two-phase composite ferroelectric ceramic of the present invention has a perovskite two-phase composite structure, which is beneficial for improving energy storage performance under high electric fields.

[0008] Furthermore, the specific value of x can be 0.1, 0.15, or 0.2. Preferably, when x=0.15, the energy storage efficiency of the ceramic material is ≥85%, and the energy storage density is 30.7 J / cm2 under an electric field of 115 MV / m. 3 , the energy storage efficiency is 85%.

[0009] When 0≤x≤0.1, the ceramic material is a perovskite single phase.

[0010] In a second aspect, a method for preparing the perovskite structure two-phase composite ferroelectric ceramic material according to the first aspect is provided, comprising the following steps:

[0011] S1, according to (0.6-x)Bi 0.5 Na 0.5 TiO3-0.4BaTiO3-xCaZrO3 (0.1≤x≤0.2) Weigh Bi2O3, Na2CO3, BaCO3, CaCO3, TiO2, and ZrO2 in a stoichiometric ratio and pour them into a ball mill jar. Add an organic solvent and perform a ball milling.

[0012] S2, drying and grinding the mixture after the first ball milling, and then calcining;

[0013] S3, ball milling and drying the calcined powder for the second time;

[0014] S4, mixing the powder obtained after secondary ball milling and drying with a sintering aid, adding a binder, grinding, granulating, sieving, and pressing into a green body;

[0015] S5. Debinding and sintering the green body to obtain the ceramic material.

[0016] Preferably, the organic solvent in S1 is anhydrous ethanol.

[0017] Preferably, the time for the first ball milling in S1 is 12-16 h, and the ball milling speed is 300-500 rpm.

[0018] Preferably, the calcination temperature in S2 is 800-900° C., the calcination time is 2-3 h, and the calcination is carried out in a muffle furnace.

[0019] Preferably, the secondary ball milling time in S3 is 12-16 h, and the ball milling speed is 300-500 rpm.

[0020] Preferably, the sintering aid in S4 is Sm2O3, and the amount of the sintering aid added is 1% of the mass of the powder obtained after secondary ball milling and drying.

[0021] Preferably, the binder in S4 is a polyvinyl alcohol aqueous solution with a mass fraction of 3%-5%, and the mass ratio of the binder to the powder obtained after secondary ball milling and drying is 1:(5-15).

[0022] Preferably, the sieving in S4 uses a sieve with a pore size of 400-500 mesh, preferably 500 mesh.

[0023] Furthermore, the green body in S5 can be placed in a crucible and put into a muffle furnace for debinding and sintering.

[0024] Preferably, the binder removal temperature in S5 is 500-600°C, the binder removal time is 2-3 h, and the heating rate is 3-5°C / min.

[0025] Preferably, the sintering temperature in S5 is 1100-1200° C., the sintering time is 1-3 h, and the heating rate is 3-5° C. / min.

[0026] In a third aspect, an application of the perovskite structure two-phase composite ferroelectric ceramic material described in the first aspect in a dielectric capacitor is provided.

[0027] The beneficial effects of the above technical solution of the present invention are as follows:

[0028] The present invention proposes to use the spinodal decomposition strategy to generate fine perovskite dual-phase composite relaxor ferroelectric ceramics in perovskite structure (ABO3) materials and achieve high energy storage performance. First, select (1-x) (Bi 0.5 Na 0.5 )TiO3-xBaTiO3 (BNT-BT) solid solution as the matrix, which has a very strong long-range FE tetragonal (T) distortion in lead-free systems and allows to obtain high P m In particular, the introduction of CaZrO3 (CZ) is based on the following theory: Ca 2+(R = 1.34 Å) and Ba 2+ The large size mismatch between the two (R = 1.61 Å) is conducive to phase separation, and the introduction of Zr with a large ionic radius and a suitable content ratio at the B site 4+ ions increase local chemical disorder. 2+ and Zr 4+ This disrupts the long-range, ordered macroscopic ferroelectric domains within the two-phase grains, forming polar nanodomains. This enhances the electric field response while effectively reducing the energy loss associated with domain reversal, resulting in both perovskite phases exhibiting typical relaxor ferroelectric characteristics. Furthermore, the refined microstructure produced by spinodal decomposition enhances the breakdown electric field by increasing the volume fraction of high-resistivity grain boundaries. Since each phase in the two-phase composite is a perovskite structure with a strong polarizability, high polarizability can be maintained on a macroscopic scale.

[0029] Thanks to the design of spinodal decomposition and the perovskite two-phase composite structure, the relaxor ferroelectric ceramics of the present invention have high breakdown field strength and high polarization strength. Ultimately, under an electric field of 115 MV / m, the energy storage density can reach 30.7 J / cm 3 , the energy storage efficiency can reach 85%, achieving excellent results. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 XRD patterns of the perovskite composite relaxor ferroelectric ceramics of Comparative Examples 1-2 and Examples 1-3;

[0032] Figure 2 This is the hysteresis loop of the perovskite two-phase composite relaxor ferroelectric ceramic of Example 2;

[0033] Figure 3 The curve showing the change of energy storage performance of the perovskite two-phase composite relaxor ferroelectric ceramic as a function of applied electric field in Example 2;

[0034] Figure 4 This is the SEM image of the perovskite two-phase composite relaxor ferroelectric ceramic of Example 2;

[0035] Figure 5 This is the EDS image of the perovskite two-phase composite relaxor ferroelectric ceramic of Example 2. DETAILED DESCRIPTION

[0036] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0037] Example 1

[0038] Preparation of (0.6-x)Bi by the method of the present invention 0.5 Na 0.5 TiO3-0.4BaTiO3-xCaZrO3 (x = 0.1). Bi2O3, Na2CO3, BaCO3, CaCO3, TiO2, and ZrO2 were weighed according to the stoichiometric ratio and poured into a ball mill. 250 ml of ethanol was added and the sample was ball milled for 12 hours at 400 rpm. The ball-milled sample was dried, ground, and then calcined in a muffle furnace at 850°C for 2 hours. The calcined powder was poured into a ball mill and ball milled for a second time for 12 hours at 400 rpm. After drying, a 5 wt% aqueous solution of polyvinyl alcohol (PVA) was added as a binder (the binder to sample ratio was 1:10). The sample was ground and granulated, and then sieved through a 500-mesh sieve. The sieved powder was pressed into a green body using a φ=10 mm mold and placed in a muffle furnace for debinding. The heating rate was 5 ℃ / min, the debinding temperature was 550 ℃, and the time was 2 h. The temperature was then increased for sintering. The heating rate was 5 ℃ / min, the sintering temperature was 1190 ℃, and the time was 2 h. After cooling, a perovskite two-phase composite relaxor ferroelectric ceramic with excellent dielectric energy storage performance was obtained.

[0039] To test the energy storage performance, the ceramic sheet was polished to a thickness of 50 μm. Gold electrodes were then plated on the upper and lower surfaces of the ceramic using an ion sputtering instrument. The ion sputtering conditions included a gold target, a current of 10 mA, and a duration of 300 s.

[0040] The test shows that the perovskite two-phase composite relaxor ferroelectric ceramic prepared in this embodiment has an energy storage density of 11 J / cm2 under an electric field of 70 MV / m. 3 , the energy storage efficiency reached 84.7%.

[0041] Example 2

[0042] The method of Example 1 is followed, except that the chemical formula of the ceramic material is: (0.6-x)Bi 0.5 Na 0.5 TiO30.4BaTiO3-xCaZrO3(x=0.15).

[0043] Example 3

[0044] The method of Example 1 is followed, except that the chemical formula of the ceramic material is: (0.6-x)Bi 0.5 Na 0.5 TiO30.4BaTiO3-xCaZrO3(x=0.2).

[0045] The test shows that the maximum polarization of the perovskite two-phase composite relaxor ferroelectric ceramic prepared in this embodiment reaches 4.1 μC / cm under an electric field of 10 MV / m. 2 , the remnant polarization is 0.07 μC / cm 2 .

[0046] Comparative Example 1

[0047] The method of Example 1 is followed, except that the chemical formula of the ceramic material is: (0.6-x)Bi 0.5 Na 0.5 TiO30.4BaTiO3-xCaZrO3(x=0).

[0048] The test shows that the perovskite single-phase relaxor ferroelectric ceramic prepared in this comparative example has a maximum polarization of 26.9 μC / cm under an electric field of 9 MV / m. 2 , the remnant polarization is 15.9 μC / cm 2 Its XRD spectrum shows that all perovskite characteristic peaks are single diffraction peaks.

[0049] Comparative Example 2

[0050] The method of Example 1 is followed, except that the chemical formula of the ceramic material is: (0.6-x)Bi 0.5 Na 0.5 TiO30.4BaTiO3-xCaZrO3(x=0.05).

[0051] The test shows that the energy storage density of the perovskite single-phase relaxor ferroelectric ceramic prepared in this comparative example reaches 8.95 J / cm under an electric field of 70 MV / m. 3 , the energy storage efficiency reaches 76.3%. Its XRD spectrum shows that all perovskite characteristic peaks are single diffraction peaks.

[0052] Figure 1XRD patterns of relaxor ferroelectric ceramics prepared in Comparative Examples 1-2 and Examples 1-3, with x being 0, 0.05, 0.1, 0.15, and 0.2, respectively. As can be seen from the figure, the characteristic peaks of the perovskites in Comparative Examples 1 and 2 are both single diffraction peaks. The characteristic peaks of the perovskites in Examples 1-3 all have two diffraction peaks, indicating that two perovskite phases have been formed, and the peak intensity of the second phase gradually increases with the increase of x. This is because the doping of CaZrO3 has a significant effect on the phase structure of the ferroelectric ceramic, and this two-phase composite structure gives it a high breakdown electric field strength.

[0053] Figure 2 The unipolar hysteresis loop of the x=0.15 perovskite two-phase composite relaxor ferroelectric ceramic prepared in Example 2 is shown. The material exhibits ferroelectric polarization characteristics of high breakdown electric field, large polarization value and small hysteresis, resulting in high energy storage efficiency and large energy storage density.

[0054] Figure 3 The energy storage performance of the x=0.15 perovskite two-phase composite relaxor ferroelectric ceramic prepared in Example 2 changes with the applied electric field. As can be seen from the figure, the perovskite two-phase composite relaxor ferroelectric ceramic described in this application exhibits high energy storage efficiency, which can be stabilized at more than 85%; and under an electric field of 115 MV / m, the energy storage density can reach 30.7 J / cm 3 , the energy storage efficiency can reach 85%.

[0055] Figure 4 This is a backscattered SEM image of the x=0.15 perovskite two-phase composite relaxor ferroelectric ceramic prepared in Example 2. It can be seen that the contrast of the two phase grains is different, and the dark area is randomly scattered with second phase grains. The grain size ranges from 0.16 to 1.39 μm, with an average grain size of 0.66 μm.

[0056] Figure 5 for Figure 4 EDS diagram of the Ca element enriched area. Figure 4 The dark grains in the figure correspond one to one, proving that the two phases of perovskite are distributed in different grains. This distribution adds a grain boundary phase composed of two grains transitioning together to the original single grain boundary phase, thereby enhancing the breakdown strength of the material.

[0057] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A perovskite structure two-phase composite ferroelectric ceramic material with excellent dielectric energy storage, characterized in that: Its chemical formula is (0.6-x)Bi 0.5 Na 0.5 TiO3-0.4BaTiO3-xCaZrO3, 0.1≤x≤0.2, the ceramic material has two composite perovskite phases.

2. The perovskite structure two-phase composite ferroelectric ceramic material with excellent dielectric energy storage according to claim 1, characterized in that: x is 0.1, 0.15 or 0.

2.

3. The perovskite structure two-phase composite ferroelectric ceramic material with excellent dielectric energy storage according to claim 2, characterized in that: When x=0.15, the energy storage efficiency of the ceramic material is ≥85%, and the energy storage density is 30.7 J / cm under an electric field of 115 MV / m. 3 , the energy storage efficiency is 85%.

4. The method for preparing the perovskite structure two-phase composite ferroelectric ceramic material according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1, according to (0.6-x)Bi 0.5 Na 0.5 TiO3-0.4BaTiO3-xCaZrO3 (0.1≤x≤0.2) Weigh Bi2O3, Na2CO3, BaCO3, CaCO3, TiO2, and ZrO2 in a stoichiometric ratio and pour them into a ball mill jar. Add an organic solvent and perform a ball milling. S2, drying and grinding the mixture after the first ball milling, and then calcining; S3, ball milling and drying the calcined powder for the second time; S4, mixing the powder obtained after secondary ball milling and drying with a sintering aid, adding a binder, grinding, granulating, sieving, and pressing into a green body; S5. Debinding and sintering the green body to obtain the ceramic material.

5. The method for preparing the perovskite structure two-phase composite ferroelectric ceramic material according to claim 4, characterized in that: The ball milling time in S1 is 12-16 h, and the ball milling speed is 300-500 rpm.

6. The method for preparing the perovskite structure two-phase composite ferroelectric ceramic material according to claim 4, characterized in that: The calcination temperature in S2 is 800-900° C., the calcination time is 2-3 h, and the calcination is carried out in a muffle furnace.

7. The method for preparing the perovskite structure two-phase composite ferroelectric ceramic material according to claim 4, characterized in that: The secondary ball milling time in S3 is 12-16 h, and the ball milling speed is 300-500 rpm.

8. The method for preparing the perovskite structure two-phase composite ferroelectric ceramic material according to claim 4, characterized in that: The sintering aid in S4 is Sm2O3, and the amount of the sintering aid added is 1% of the mass of the powder obtained after secondary ball milling and drying; The binder in S4 is a polyvinyl alcohol aqueous solution with a mass fraction of 3%-5%, and the mass ratio of the binder to the powder obtained after secondary ball milling and drying is 1:(5-15).

9. The method for preparing the perovskite structure two-phase composite ferroelectric ceramic material according to claim 4, characterized in that: The binder removal temperature in S5 is 500-600 °C, the binder removal time is 2-3 h, and the heating rate is 3-5 °C / min; The sintering temperature in S5 is 1100-1200°C, the sintering time is 1-3 h, and the heating rate is 3-5°C / min.

10. Use of the perovskite structure two-phase composite ferroelectric ceramic material according to any one of claims 1 to 3 in dielectric capacitors.

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