Relaxation ferroelectric ceramic material with polar vortex structure as well as preparation method and application of relaxation ferroelectric ceramic material

Abstract

The invention relates to the technical field of inorganic nonmetal functional ceramic materials, and discloses a polar vortex structure relaxor ferroelectric ceramic material and a preparation method and application thereof, the chemical formula of the material is (1-x) (0.7 NaNbO3-0. 3Sr0. 7Bi0. 2TiO3)-xCaSnO3, x is more than or equal to 0 and less than or equal to 0.2, and the characteristic value is x = 0.1. The preparation method comprises the following steps: synthesizing NaNbO3, Sr0. 7Bi0. 2TiO3 and CaSnO3 ceramic powder in advance by adopting a step-by-step solid-phase reaction method, carrying out ball-milling mixing according to a stoichiometric ratio, and sintering to obtain the ceramic. The prepared ceramic material has a multiphase coexistence, core-shell and polar vortex structure, shows high saturation polarization intensity, low hysteresis, large breakdown field strength and excellent service stability, and has potential application in high-power pulse devices. The material is environment-friendly, the process is simple, and a new technical path is expected to be provided for design and preparation of a high-performance and high-stability nonlinear dielectric energy storage material.

Description

Technical Field

[0001] The invention relates to the technical field of inorganic non-metallic functional ceramic materials, and more specifically to a polar vortex structure relaxor ferroelectric ceramic material, a preparation method and application thereof in high-power pulse devices. Background Art

[0002] Dielectric capacitors have the characteristics of ultrafast energy conversion rate, high reliability and environmental friendliness. They are widely used in energy and power, electronic circuit systems, and are irreplaceable basic components in high-power pulse technology. They can achieve instantaneous energy release and power amplification, and are of great strategic demand in ultra-high power equipment and related cutting-edge scientific research. Relaxors are favored by researchers because of their unique nanodomain structure and diffuse phase change characteristics, which are expected to provide support for the creation and application of wide temperature range, high-performance nonlinear dielectric energy storage materials. However, the rapid polarization saturation behavior of relaxors results in relatively low saturation polarization, which also hinders their high performance development.

[0003] At present, the improvement of nonlinear dielectric energy storage properties is mostly focused on the regulation of polar region size, which usually achieves high energy storage efficiency at the expense of saturation polarization intensity. Topological polar vortex structure can enhance dielectric relaxation and reduce residual polarization intensity, achieving a synergistic improvement in energy storage density and efficiency. Under normal circumstances, electric dipoles tend to be arranged in parallel to form mediocre domains rather than rotate to form topological structures; and the anisotropy of dielectric materials is usually stronger than that of magnetic materials, so the driving force required to rotate electric dipoles to form topological structures is greater. Topological polar structures are not stable. If there are no suitable boundary conditions to maintain them, they will relax back to mediocre domain structures. Therefore, the preparation window and stable existence window of polar topological structures are relatively narrow. Ferroelectric thin film materials are affected by substrates, preparation processes, etc., and have non-negligible stress and high-density grain boundaries. Topological polar structures can be easily obtained by modulating elastic energy and electrostatic energy. In comparison, constructing ferroelectric ceramic polar vortex structures is extremely challenging. Summary of the invention

[0004] In view of this, the present invention aims at the problem that the rapid polarization saturation behavior of the relaxor leads to relatively low saturation polarization, and proposes a polar vortex structure relaxor ferroelectric ceramic material and a preparation method and application thereof.

[0005] It should be noted that the researchers used phase field simulation to simulate the domain structures of grain boundaries with different dielectric constants and different concentrations, and found that the depolarization field induced by high-concentration low-dielectric constant grain boundaries can promote the formation of polar vortex structures. This theoretical prediction shows that polar vortex structures can be constructed by regulating the core-shell structure or grain boundary density of ferroelectric ceramics.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] The first technical purpose of the present invention is to provide a polar vortex structure relaxor ferroelectric ceramic material, the chemical formula of which is (1-x)(0.7NaNbO 3 -0.3Sr 0.7 Bi 0.2 TiO 3 )-xCaSnO 3 , where 0≤x≤0.2.

[0008] Furthermore, the characteristic value of the chemical formula of the material is: x=0.1.

[0009] The second technical purpose of the present invention is to provide a method for preparing a polar vortex structure relaxor ferroelectric ceramic material, by pre-synthesizing NaNbO by a step-by-step solid phase reaction method. 3 , Sr 0.7 Bi 0.2 TiO 3 、CaSnO 3 The ceramic powder is then ball-milled and mixed according to the stoichiometric ratio and sintered into porcelain.

[0010] Furthermore, the NaNbO 3 The pre-synthesis temperature of the ceramic powder is 850-900°C, and the time is 3-5h.

[0011] Furthermore, the Sr 0.7 Bi 0.2 TiO 3 The pre-synthesis temperature of the ceramic powder is 900-1000°C, and the time is 3-5h.

[0012] Furthermore, the CaSnO 3 The pre-synthesis temperature of the ceramic powder is 1000-1050°C, and the time is 3-5h.

[0013] Furthermore, the (1-x)(0.7NaNbO 3 -0.3Sr 0.7 Bi 0.2 TiO 3 )-xCaSnO 3 The sintering heating rate of the ceramic material is 1-10°C / minute, the sintering temperature is 1200-1400°C, and the sintering time is 3-5h.

[0014] The third technical purpose of the present invention is to provide an application of the polar vortex structure relaxor ferroelectric ceramic material as described above in high-power pulse devices.

[0015] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. The present invention defines that the material has P21 ma, Pnma 2 , Pbnm, P4 / mbm and P4 2 / mnmSnO 2 Multiphase coexistence, core-shell and polar vortex structures show high saturation polarization intensity, low hysteresis, large breakdown field strength and excellent service stability, and have potential applications in high-power pulse devices.

[0017] 2. The material of the present invention is environmentally friendly and has a simple process, and is expected to provide a new technical path for the design and preparation of high-performance, high-stability nonlinear dielectric energy storage materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0019] Figure 1 (1-x)(0.7NaNbO 3 -0.3Sr 0.7 Bi 0.2 TiO 3 )-xCaSnO 3 PE curve of ceramic material (a) at 360 kV / cm electric field and (b) at maximum breakdown field strength, and (c) energy storage density and efficiency at maximum breakdown field strength.

[0020] Figure 2 0.63NaNbO 3 -0.27Sr 0.7 Bi 0.2 TiO 3 -0.1CaSnO 3 (a) X-ray diffraction refinement pattern and (b) transmission electron microscope imaging photograph of ceramic materials.

[0021] Figure 3 0.63NaNbO 3 -0.27Sr 0.7 Bi 0.2 TiO 3 -0.1CaSnO 3 (a) Transmission electron microscope imaging of grain boundaries of ceramic materials and (b) energy spectrum line scanning element content analysis.

[0022] Figure 4 0.63NaNbO 3 -0.27Sr 0.7Bi 0.2 TiO 3 -0.1CaSnO 3 (a) High-angle annular dark-field transmission electron microscope imaging photograph and polar atomic displacement map of ceramic materials and (b) representative local magnification image and simulation image.

[0023] Figure 5 0.63NaNbO 3 -0.27Sr 0.7 Bi 0.2 TiO 3 -0.1CaSnO 3 PE curves of ceramic materials at (a) different frequencies, (b) different temperatures, (c) different numbers of cycles and (df) the corresponding energy storage density and efficiency. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Raw material source: Na 2 CO 3 (98.0%, Alfa Aesar (Tianjin) Chemical Co., Ltd.), CaCO 3 (99.0%, Sinopharm Shanghai Chemical Reagent Co., Ltd.), SrCO 3 (97.5%, Alfa Aesar (Tianjin) Chemical Co., Ltd.), Bi 2 O 3 (99.0%, Sinopharm Shanghai Chemical Reagent Co., Ltd.), TiO 2 (99.5%, Alfa Aesar (Tianjin) Chemical Co., Ltd., Nb 2 O 5 (99.9%, Sinopharm Shanghai Chemical Reagent Co., Ltd.) and SnO 2 (99.0%, Sinopharm Shanghai Chemical Reagent Co., Ltd.).

[0026] The present invention relates to (1-x)(0.7NaNbO 3 -0.3Sr 0.7 Bi 0.2 TiO 3 )-xCaSnO 3 The ceramic material preparation process is as follows:

[0027] (1) Weigh the required oxide or carbonate according to the stoichiometric ratio, then place the weighed raw materials in a tetrafluoroethylene ball mill for wet grinding for 8 hours, and then discharge, dry and pre-sinter at 850-900°C, 900-1000°C, and 1000-1050°C for 3-5 hours to obtain NaNbO 3 , Sr 0.7 Bi 0.2 TiO 3 、CaSnO 3 Ceramic powder;

[0028] (2) weighing the ceramic powder according to the stoichiometric ratio, ball milling, discharging, and drying the mixed powder, and then granulating the mixed powder with polyvinyl alcohol having a mass concentration of 8 to 10% as a binder, and pressing the mixed powder into a ceramic green sheet through a forming mold at a pressure of 10 to 100 MPa;

[0029] (3) The ceramic green sheet was subjected to a debonding treatment at 550-600°C, and then heated to 1200-1400°C at a heating rate of 1-10°C / min and sintered for 3-5h to obtain (1-x)(0.7NaNbO 3 -0.3Sr 0.7 Bi 0.2 TiO 3 )-xCaSnO 3 Ceramic material.

[0030] Example 1

[0031] The required oxide or carbonate was weighed according to the stoichiometric ratio, and the weighed raw materials were placed in a tetrafluoroethylene ball mill for wet grinding for 8 hours, and then discharged, dried and pre-calcined at 900℃ for 5 hours, 940℃ for 4 hours, and 1000℃ for 3 hours to obtain NaNbO 3 , Sr 0.7 Bi 0.2 TiO 3 、CaSnO 3 The ceramic powder is weighed according to the stoichiometric ratio, ball-milled, discharged, and dried, and then the mixed powder is granulated with 8-10% polyvinyl alcohol as a binder, and pressed into a ceramic green sheet through a forming mold at 20MPa; the ceramic green sheet is debonded at 550-600°C, and then sintered at 1380°C at a heating rate of 3°C / min for 3h to obtain (1-x)(0.7NaNbO 3 -0.3Sr 0.7 Bi 0.2 TiO 3 )-xCaSnO 3 Ceramic materials, where x=0, 0.05, 0.1, 0.15, 0.2.

[0032] Figure 1(1-x)(0.7NaNbO 3 -0.3Sr 0.7 Bi 0.2 TiO 3 )-xCaSnO 3 The PE curve of ceramic materials under 360kV / cm electric field and maximum breakdown field strength, as well as the energy storage density and efficiency under maximum breakdown field strength. The results show that the PE curve of ceramic materials increases with the increase of CaSnO 3 The content of the curve gradually evolved into a linear curve, and the maximum breakdown field strength of the optimal component x = 0.1 was as high as 752 kV cm -1 , the corresponding releasable energy storage density W rec and efficiency η reached 6.83±0.18 J cm -3 with 95.7±1.0%.

[0033] Example 2

[0034] Select the characteristic value x = 0.1, that is, 0.63NaNbO 3 -0.27Sr 0.7 Bi 0.2 TiO 3 -0.1CaSnO 3 Ceramic materials, analysis of their microstructure and service stability.

[0035] Figure 2 0.63NaNbO 3 -0.27Sr 0.7 Bi 0.2 TiO 3 -0.1CaSnO 3 X-ray diffraction refinement of ceramic materials and transmission electron microscope imaging photos show that the ceramic material has P2 1 ma, Pnma 2 , Pbnm, P4 / mbm and P4 2 / mnmSnO 2 Multiphase coexistence and core-shell structured grains.

[0036] Figure 3 0.63NaNbO 3 -0.27Sr 0.7 Bi 0.2 TiO 3 -0.1CaSnO 3 Transmission electron microscope imaging of the grain boundaries of ceramic materials and analysis of element content by energy spectrum line scanning show the presence of Ca-, Sn- and Bi-rich phases at the ceramic grain boundaries.

[0037] Figure 4 0.63NaNbO3 -0.27Sr 0.7 Bi 0.2 TiO 3 -0.1CaSnO 3 High-angle annular dark-field transmission electron microscope imaging photographs and polar atomic displacement maps of ceramic materials as well as representative local magnification images and simulation images show the existence of local disordered areas and polar vortex structures.

[0038] Figure 5 0.63NaNbO 3 -0.27Sr 0.7 Bi 0.2 TiO 3 -0.1CaSnO 3 Ceramic materials at 500752kV cm -1 PE curves and corresponding energy storage density and efficiency at different frequencies, temperatures, and cycle times under electric fields. The results show that within the frequency range of 10 to 200 Hz, W rec and efficiency η are 3.41±0.07Jcm -3 98.1±1.5% in the temperature range of room temperature to 150℃ rec and efficiency η are 3.14±0.34Jcm -3 and 93.6±7.0%, in 1~10 5 Within the cycle number range W rec and efficiency η were 3.56±0.03Jcm -3 With 97.6±1.4%, it shows excellent service stability.

[0039] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A polar vortex structure relaxor ferroelectric ceramic material, characterized in that: The chemical formula of the material is (1-x)(0.7NaNbO3-0.3Sr 0.7 Bi 0.2 TiO3)-xCaSnO3, where 0≤x≤0.

2.

2. The polar vortex structure relaxor ferroelectric ceramic material according to claim 1, characterized in that: In the chemical formula of the polar vortex structure relaxor ferroelectric ceramic material, x=0.

1.

3. A method for preparing the polar vortex structure relaxor ferroelectric ceramic material as claimed in claim 1, characterized in that: NaNbO3 and Sr were pre-synthesized by a step-by-step solid phase reaction method. 0.7 Bi 0.2 TiO3 and CaSnO3 ceramic powders are then ball-milled and mixed according to the stoichiometric ratio and sintered into porcelain.

4. The method for preparing the polar vortex structure relaxor ferroelectric ceramic material according to claim 3, characterized in that: The pre-synthesis temperature of the NaNbO3 ceramic powder is 850-900°C and the time is 3-5 hours.

5. The method for preparing the polar vortex structure relaxor ferroelectric ceramic material according to claim 3, characterized in that: The Sr 0.7 Bi 0.2 The pre-synthesis temperature of TiO3 ceramic powder is 900-1000°C and the time is 3-5h.

6. The method for preparing the polar vortex structure relaxor ferroelectric ceramic material according to claim 3, characterized in that: The presynthesis temperature of the CaSnO3 ceramic powder is 1000-1050°C, and the time is 3-5 hours.

7. The method for preparing the polar vortex structure relaxor ferroelectric ceramic material according to claim 3, characterized in that: The sintering heating rate of the ceramic material is 1-10°C / minute, the sintering temperature is 1200-1400°C, and the sintering time is 3-5h.

8. Use of the polar vortex structure relaxor ferroelectric ceramic material as claimed in claim 1 or the polar vortex structure relaxor ferroelectric ceramic material prepared by the method as claimed in claim 3 in high power pulse devices.

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