High-ferroelectric-stability sodium bismuth titanate-based lead-free energy storage ceramic material and preparation method thereof

Abstract

The application discloses a sodium bismuth titanate-based lead-free energy storage ceramic material with high ferroelectric stability and temperature stability and a preparation method thereof. 0.5 Na 0.5 TiO3-0.15NaNbO3)-xSrHfO3, wherein x is 0.04-0.15. The ceramic material is prepared through dosing, ball milling, pre-sintering, secondary ball milling, sieving, tabletting and sintering, and has the advantages of simple preparation method, low cost, good repeatability and high product yield. The obtained ceramic material has high ferroelectric stability (recurrent stability and frequency stability), good temperature stability and energy storage characteristics. When x=0.10, the dielectric constant is epsilon r150℃,100kHz =1065.39, the dielectric loss tan delta 150℃,100kHz =0.01472, the temperature change rate satisfies TCC 150℃ <=+ / -15% in the temperature range of 68-371 DEG C, the breakdown strength is 250kV / cm, the maximum polarization strength is 33C / cm 2 , the energy storage density is 3.05J / cm 3 , and the energy storage efficiency can reach 75.9%.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ceramic materials, and particularly relates to a sodium bismuth titanate-based lead-free energy storage ceramic material with high ferroelectric stability and temperature stability and a preparation method thereof. BACKGROUND

[0002] In recent years, with the development of science and technology, energy shortage and environmental pollution problems are increasingly prominent. With the development and utilization of renewable energy, higher demands are put forward for the energy storage and conversion efficiency, and therefore people urgently need to find new energy storage technologies and materials with high energy storage density, energy storage efficiency, environmental friendliness and low cost. Dielectric capacitors have attracted more and more researchers' attention due to their high power density, extremely fast charge and discharge rate and good temperature stability. However, the diversification of the working environment of the application field puts forward more stringent requirements for the performance parameters thereof. For example, the energy storage demand of electronic and electrical systems in harsh environments is increasing, and new high-temperature capacitor materials are required to have good temperature stability and energy storage characteristics in a wide temperature range, moderate dielectric constant and low dielectric loss. Sodium bismuth titanate (Bi 0.5 Na 0.5 TiO3) material is considered to have great energy storage potential due to its high saturation polarization strength and high Curie temperature.

[0003] At present, with the development of a new generation of lead-free dielectric energy storage materials, it is still difficult to obtain ceramic energy storage materials with high ferroelectric stability, energy storage characteristics, temperature stability and low dielectric loss. Therefore, how to realize the synergistic regulation of high ferroelectric stability, energy storage characteristics and temperature stability in sodium bismuth titanate-based lead-free energy storage ceramic materials has important research and application significance. SUMMARY

[0004] The technical problem to be solved by the present application is to overcome the difficulty in realizing the synergistic regulation of high ferroelectric stability, energy storage characteristics and temperature stability in the existing sodium bismuth titanate-based lead-free energy storage ceramic material, and to provide a sodium bismuth titanate-based lead-free energy storage ceramic material with high ferroelectric stability and temperature stability, and to provide a simple and low-cost preparation method for the ceramic material.

[0005] To achieve the above purpose, the sodium bismuth titanate-based lead-free energy storage ceramic material provided by the present application has a structural formula of (1-x)(0.85Bi 0.5 Na 0.5 TiO3-0.15NaNbO3)-xSrHfO3, wherein x is 0.04-0.15, and preferably x is 0.10.

[0006] The ceramic material is pure perovskite structure, the breakdown field strength is 150-260kV / cm, and the maximum polarization strength is 22-41muC / cm 2 .

[0007] When the value of x is 0.10, the ceramic material has a dielectric constant of epsilon r150℃,100kHz =1065.39 and a dielectric loss tan delta 150℃,100kHz =0.01472 at 100kHz, a temperature change rate of TCC 150℃ ≤±15% in the temperature range of 68-371℃, a breakdown strength of 250kV / cm, a maximum polarization strength of 33muC / cm 2 , an effective energy storage density of 3.05J / cm 3 , and an energy storage efficiency of 75.9%.

[0008] The preparation method of the sodium bismuth titanate-based lead-free energy storage ceramic material comprises the following steps:

[0009] Step 1: according to the stoichiometric ratio of (1-x)(0.85Bi 0.5 Na 0.5 TiO3-0.15NaNbO3)-xSrHfO3, TiO2, Na2CO3, Bi2O3, HfO2, Nb2O5 and SrCO3 with a purity of more than 98.00% are weighed respectively, the weighed raw materials are uniformly mixed and then put into a nylon tank, zirconium balls are used as grinding balls, anhydrous ethanol is used as a ball milling medium, and the mixture is fully mixed and ball milled for 20-24 hours, and then dried at 60-90℃ for 20-24 hours to obtain a raw material mixture;

[0010] Step 2: the raw material mixture in step 1 is pre-fired at 850-950℃ for 2-4 hours, and then subjected to secondary ball milling, drying and sieving to obtain a (1-x)(0.85Bi 0.5 Na 0.5 TiO3-0.15NaNbO3)-xSrHfO3 mixture;

[0011] Step 3: the (1-x)(0.85Bi 0.5 Na 0.5 TiO3-0.15NaNbO3)-xSrHfO3 mixture in step 2 is pressed into a tablet, and then sintered at 1100-1210℃ for 2-4 hours, and then naturally cooled to room temperature in the furnace to prepare a sodium bismuth titanate-based lead-free energy storage ceramic material.

[0012] In the above step 2, the raw material mixture of step 1 is preferably pre-fired at 850-950℃ for 2-4 hours, the obtained powder is then loaded into a nylon tank, mixed and ball milled for 20-24 hours, dried at 60-90℃ for 12-24 hours, ground by a mortar and sieved through a 180-200 mesh screen.

[0013] In the above step 3, the tablet pressing is preferably performed by a powder tablet press to form a cylindrical blank, which is then cold isostatic pressed at a pressure of 150-200MPa for 5-7 minutes.

[0014] In the above step 3, the cylindrical blank after cold isostatic pressing is preferably placed on a zirconia flat plate, and sintered by a buried firing method, wherein the zirconia flat plate is placed in an alumina closed sagger, and heated at a rate of 2-5℃ / min to 1100-1210℃, and sintered at constant temperature for 2-4 hours.

[0015] The beneficial effects of the present application are as follows:

[0016] 1. The present application substitutes Sr 0.5 Na 0.5 TiO3-0.15NaNbO3 system with Sr 2+ / Hf 4+ ion doping, which destroys the long-range ordered ferroelectric domains, constructs the coexistence of R3c and P4bm phases, and makes the obtained ceramic material have high ferroelectric stability, energy storage characteristics, temperature stability and low dielectric loss. When x=0.10, the material has the highest effective energy storage density and energy storage efficiency, which are 3.05J / cm 3 and 75.9%, respectively, and the dielectric breakdown field strength is 260kV / cm. The material has extremely low dielectric loss (tan 100kHz <0.025) in the medium-low temperature range of 40-390℃, and the low dielectric loss temperature range is widened.

[0017] 2. The preparation method of the present application is simple, reproducible and practical, and provides a new material system with development potential for lead-free energy storage ceramic materials with high ferroelectric stability, low dielectric loss and temperature stability. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is the XRD pattern of the ceramic material prepared in Comparative Example 1 and Examples 1-5.

[0019] Figure 2 is the dielectric constant and dielectric loss diagram of the ceramic material prepared in Comparative Example 1 at different test frequencies.

[0020] Figure 3 is the dielectric constant and dielectric loss diagram of the ceramic material prepared in Example 4 at different test frequencies.

[0021] Figure 4The ceramic materials prepared in Comparative Example 1 and Examples 1-5 showed Δε / ε at 100 kHz. 150℃ The curve showing how the temperature changes with temperature T.

[0022] Figure 5 The ceramic materials prepared in Comparative Example 1 and Examples 1-5 are compared in ε 150℃,100kHz±15％ Temperature range graph.

[0023] Figure 6 This is a unipolar hysteresis loop diagram of the ceramic materials prepared in Comparative Example 1 and Examples 1-5 under the critical breakdown electric field.

[0024] Figure 7 This is a unipolar PE curve of the ceramic material prepared in Example 4 at different cycles.

[0025] Figure 8 This is a unipolar PE curve of the ceramic material prepared in Example 4 at different frequencies.

[0026] Figure 9 This is a comparison chart of the effective energy storage density, total energy storage density, and energy storage efficiency of the ceramic materials prepared in Comparative Example 1 and Examples 1-5 under the critical breakdown electric field. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited to these embodiments.

[0028] Comparative Example 1

[0029] Step 1: According to 0.85Bi 0.5 Na 0.5 To determine the stoichiometry of TiO3-0.15NaNbO3, 2.9506g of Na2CO3, 9.6651g of Bi2O3, 6.2795g of TiO2, and 1.8440g of Nb2O5 with a purity of ≥99.00% were weighed out. All the weighed raw materials were mixed evenly and placed in a nylon can. Using zirconium balls as grinding balls and anhydrous ethanol as the grinding medium, the mixture was ball-milled for 24 hours at a speed of 401 rpm. After drying at 80℃ for 24 hours, the mixture was ground in a mortar and pestle for 30 minutes to obtain the raw material mixture.

[0030] Step 2: Place the raw material mixture from Step 1 into an alumina crucible, gently compact it with an agate rod, cover it, and place it in a resistance furnace. Pre-calcine at 850°C for 3 hours at a heating rate of 3°C / min. Allow it to cool naturally to room temperature, remove it from the furnace, and grind it in a mortar and pestle for 40 minutes to obtain pre-calcined powder. Place the pre-calcined powder into a nylon can, mix thoroughly, and ball-mill for 24 hours. Dry it at 80°C for 12 hours, grind it in a mortar and pestle, and pass it through an 180-mesh sieve to obtain 0.85Bi. 0.5 Na0.5 TiO3-0.15NaNbO3 mixture.

[0031] Step 3: 0.85Bi 0.5 Na 0.5 The TiO3-0.15NaNbO3 mixture was pressed into a cylindrical green body with a diameter of 11.5 mm and a thickness of 1.1 mm by a powder tablet press, and then cold isostatic pressed at a pressure of 190 MPa for 5 minutes. The cylindrical green body was placed on a zirconia flat plate, and an alumina flat plate was placed in an alumina closed crucible, and then heated to 1150°C at a heating rate of 3°C / min, and sintered at a constant temperature for 3 hours, and then naturally cooled to room temperature in the furnace, to prepare a ceramic material of 0.85Bi 0.5 Na 0.5 TiO3-0.15NaNbO3.

[0032] Example 1

[0033] In Step 1 of this example, 0.96 (0.85Bi 0.5 Na 0.5 TiO3-0.15NaNbO3)-0.04SrHfO3 stoichiometry, 0.7707 g of HfO2 with a purity of 98.00% or more and 2.7610 g of Na2CO3, 5.8760 g of TiO2, 9.0441 g of Bi2O3, 1.7255 g of Nb2O5, and 0.5300 g of SrCO3 with a purity of 99.00% or more were weighed, and the other steps were the same as those of Comparative Example 1, to prepare a ceramic material of 0.94 (0.85Bi 0.5 Na 0.5 TiO3-0.15NaNbO3)-0.04SrHfO3.

[0034] Example 2

[0035] In Step 1 of this example, 0.94 (0.85Bi 0.5 Na 0. 5TiO3-0.15NaNbO3)-0.06SrHfO3 stoichiometry, 1.1417 g of HfO2 with a purity of 98.00% or more and 2.6697 g of Na2CO3, 5.6818 g of TiO2, 8.7452 g of Bi2O3, 1.6685 g of Nb2O5, and 0.7851 g of SrCO3 with a purity of 99.00% or more were weighed, and the other steps were the same as those of Comparative Example 1, to prepare a ceramic material of 0.90 (0.85Bi 0.5 Na 0.5 TiO3-0.15NaNbO3)-0.06SrHfO3.

[0036] Example 3

[0037] In Step 1 of this example, 1.5035 g of HfO2 having a purity of 98.00% or more and 2.5807 g of Na2CO3 having a purity of 99.00% or more, 5.4924 g of TiO2, 8.4537 g of Bi2O3, 1.6128 g of Nb2O5, and 1.0339 g of SrCO3 having a purity of 99.00% or more were weighed according to the stoichiometry of 0.92(0.85Bi 0.5 Na 0.5 TiO3-0.15NaNbO3)-0.08SrHfO3, and the other steps were identical to those of Comparative Example 1, thereby preparing a ceramic material of the molecular formula 0.92(0.85Bi 0.5 Na 0.5 TiO3-0.15NaNbO3)-0.08SrHfO3.

[0038] Example 4

[0039] In Step 1 of this example, 1.8564 g of HfO2 having a purity of 98.00% or more and 2.4939 g of Na2CO3 having a purity of 99.00% or more, 5.3076 g of TiO2, 8.1692 g of Bi2O3, 1.5586 g of Nb2O5, and 1.2766 g of SrCO3 having a purity of 99.00% or more were weighed according to the stoichiometry of 0.90(0.85Bi 0.5 Na 0.5 TiO3-0.15NaNbO3)-0.10SrHfO3, and the other steps were identical to those of Comparative Example 1, thereby preparing a ceramic material of the molecular formula 0.90(0.85Bi 0.5 Na 0.5 TiO3-0.15NaNbO3)-0.10SrHfO3.

[0040] Example 5

[0041] In Step 1 of this example, 2.7024 g of HfO2 having a purity of 98.00% or more and 2.2858 g of Na2CO3 having a purity of 99.00% or more, 4.8647 g of TiO2, 7.4876 g of Bi2O3, 1.4285 g of Nb2O5, and 1.8584 g of SrCO3 having a purity of 99.00% or more were weighed according to the stoichiometry of 0.85(0.85Bi 0.5 Na 0.5 TiO3-0.15NaNbO3)-0.15SrHfO3, and the other steps were identical to those of Comparative Example 1, thereby preparing a ceramic material of the molecular formula 0.85(0.85Bi 0.5 Na 0.5Ceramic material of TiO3-0.15NaNbO3-0.15SrHfO3.

[0042] The ceramic materials prepared in the above Examples 1-5 and Comparative Example 1 were each selected one surface, sanded with 320 mesh sandpaper, then sanded to 0.5 mm with 800 mesh sandpaper, and finally polished to 0.15 mm thick with 1500 mesh sandpaper and diamond sand, ultrasonically cleaned with alcohol and sputtered with gold electrodes for ferroelectric property testing. The samples were sanded, polished, ultrasonically cleaned, and wiped clean, and silver paste was applied to the upper and lower surfaces, placed in a muffle furnace at 900°C for 3 hours, and naturally cooled to room temperature for dielectric property testing. XRD testing was performed using a Japan Rigaku MiniFlex600 diffractometer, DMS-2000 high-temperature dielectric impedance spectrometer produced by Biliabo Technology Co., Ltd., and a ferroelectric tester produced by the United States Radiant company to characterize and test the structure and properties, and the results are shown in Figures 1-9 .

[0043] From Figure 1 it can be seen that all the ceramics are perovskite structures, and no second phase is observed, indicating that the third component SrHfO3 has completely solid-solved into the 0.85Bi 0.5 Na 0.5 TiO3-0.15NaNbO3 lattice. From Figures 2-3 , the dielectric temperature spectra of the ceramic materials of Comparative Example 1 and Example 4, respectively, the test temperature range is -150-400°C. With the increase of the SrHfO3 doping amount, the Curie temperature moves not obviously, the relaxivity of the ceramic material doped with SrHfO3 is enhanced, and the dielectric loss is reduced. Figures 4-5 shows the curve of Δε / ε 150℃ of the ceramic material versus temperature T and the temperature range of the material at ε 150℃,100kHz±15％ , it is generally considered that the rate of change of the dielectric constant does not exceed 15%, i.e. it indicates that the dielectric constant of the ceramic material has good temperature stability, the results show that the doping of SrHfO3 effectively broadens the temperature stability of the dielectric constant of the ceramic material, when x = 0.15, it has the widest temperature stability range, i.e. 56-393°C, showing good temperature stability, wherein the dielectric constant of the ceramic material of Example 4 is ε r150℃,100kHz = 1065.39, the dielectric loss tan δ 150℃,100kHz = 0.01472, and in the temperature range of 68-371°C, the temperature change rate satisfies TCC 150℃ ≤ ± 15%. From Figure 5 it can be seen that the breakdown field strength of the ceramic materials of Examples 1-5 is 150-260 kV / cm, and the maximum polarization strength is 22-41 μC / cm 2, and with the increase of the SrHfO3 doping amount, the breakdown field strength of the ceramic material prepared in Example 2 is obviously improved from 170 kV / cm of Comparative Example 1 to 220 kV / cm, the improvement of the breakdown field strength makes the energy storage density greatly improved; the ceramic material of Example 4 has slightly improved maximum polarization strength (P max ) and breakdown field strength compared with the ceramic material of Example 2, the maximum polarization strength is 33 μC / cm 2 , the breakdown strength is 250 kV / cm, at the same time, the remanent polarization (P r ) is slightly reduced, so that the ceramic material obtains high effective energy storage density and high energy storage efficiency; the ceramic material of Example 5 has reduced P max compared with the ceramic material of Example 4, so that the energy storage density is reduced. Figures 7-8 The results show that, in the range of multiple cycle tests, the ceramic material of Example 4 still has good and complete hysteresis loop without difference change, which indicates that the ceramic has extremely high cycle stability in the range of 1-5000 tests. At the same time, in a wide frequency range, the ceramic material of Example 4 still has good and complete hysteresis loop, which indicates that the ceramic has extremely high frequency stability in the frequency range of 50-500 Hz. Figure 9 The results show that the ceramic material of Example 4 has high energy storage density and energy storage efficiency, the energy storage density and the energy storage efficiency are 3.05 J / cm 3 and 75.9%, respectively. It can be seen that the ceramic material has good ferroelectric stability, energy storage characteristics and temperature stability, and is expected to provide a new alternative material system in the field of energy storage ceramic capacitors.

Claims

1. A sodium bismuth titanate-based lead-free energy storage ceramic material with high ferroelectric stability and temperature stability, characterized in that: The ceramic material has a general structure formula (1 x )(0.85Bi 0.5 Na 0.5 TiO3-0.15NaNbO3)- x SrHfO3, wherein x represents the molar ratio of SrHfO3 to the total amount of substance, x and the value of is 0.04-0.15; the ceramic material is pure perovskite structure, the breakdown field strength is 150-260 kV / cm, and the maximum polarization strength is 22-41 μC / cm 2 . The ceramic material is prepared by the following steps: Step 1: according to (1- x )(0.85Bi 0.5 Na 0.5 TiO3-0.15NaNbO3)- x SrHfO3 stoichiometric ratio, respectively, the purity of 98.00 % or more than TiO2, Na2CO3, Bi2O3, HfO2, Nb2O5, SrCO3, mixed with the weighing of all the raw materials uniformly into a nylon tank, with zirconium ball as the grinding ball, anhydrous ethanol as the ball milling medium, fully mixed ball milling 20-24 hours, drying at 60-90 ℃ for 20-24 hours, to get the raw material mixture; Step 2: The raw material mixture of step 1 is calcined at 850-950°C for 2-4 hours, ball-milled twice, dried, and sieved to obtain (1- x )(0.85Bi 0.5 Na 0.5 TiO3-0.15NaNbO3)- x SrHfO3 mixture; Step 3: (1- x )(0.85Bi 0.5 Na 0.5 TiO3-0.15NaNbO3)- x SrHfO3 mixture is sintered at a constant temperature of 1100-1210°C for 2-4 hours, and naturally cooled to room temperature with the furnace, to prepare a sodium bismuth titanate-based lead-free energy storage ceramic material; the pressing is performed by a powder tablet press to press into a cylindrical green body, and then cold isostatic pressing is performed at a pressure of 150-200 MPa for 5-7 minutes. 2.The sodium bismuth titanate-based lead-free energy storage ceramic material with high ferroelectric stability and temperature stability according to claim 1, characterized in that: x the value of 0.

10. 3.The sodium bismuth titanate-based lead-free energy storage ceramic material with high ferroelectric stability and temperature stability according to claim 2, characterized in that: The ceramic material has a dielectric constant of ε r150℃, 100kHz = 1065.39, a dielectric loss tan δ 150℃, 100kHz = 0.01472, a temperature change rate TCC 150℃ ≤ ± 15% in a temperature range of 68-371℃, a breakdown strength of 250 kV / cm, a maximum polarization strength of 33 μC / cm 2 , an effective energy storage density of 3.05 J / cm 3 , and an energy storage efficiency of 75.9%. 4.The sodium bismuth titanate-based lead-free energy storage ceramic material with high ferroelectric stability and temperature stability according to claim 1, characterized in that: In step 2, the raw material mixture of step 1 is pre-fired at 850-950°C for 2-4 hours, the obtained powder is loaded into a nylon tank, mixed and ball milled for 20-24 hours, dried at 60-90°C for 12-24 hours, ground by a mortar, and sieved through a 180-200 mesh screen. 5.The sodium bismuth titanate-based lead-free energy storage ceramic material with high ferroelectric stability and temperature stability according to claim 1, characterized in that: In step 3, the cold isostatic pressed cylindrical body is placed on a zirconia flat plate, and the zirconia flat plate is placed in an alumina closed sagger in a buried firing manner, heated to 1100-1210°C at a heating rate of 2-5°C / min, and sintered at constant temperature for 2-4 hours.

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