A strontium titanate-based relaxor ferroelectric ceramic material with high energy storage density and efficiency and a preparation method thereof

Abstract

The application belongs to the field of dielectric energy storage ceramic materials, and particularly relates to a strontium titanate-based relaxor ferroelectric ceramic material with high energy storage density and efficiency and a preparation method thereof. 0.5 Na 0.5 TiO3)‑xBaHfO3, x=0.01‑0.3. The application can reduce the remanent polarization intensity and improve the breakdown field strength while retaining the high polarization intensity, thereby improving the energy storage density and energy storage efficiency, so that the application can better meet the requirements of practical applications.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of dielectric energy storage ceramic materials, and particularly relates to a strontium titanate-based relaxor ferroelectric ceramic material with high energy storage density and efficiency and a preparation method thereof. BACKGROUND

[0002] Ferroelectric materials have the ability of electrostatic energy storage due to their spontaneous polarization, and play an increasingly important role in the field of energy storage. Lead-based ferroelectric ceramics have the advantages of large polarization strength, and have a large advantage in energy storage density and its application, but the use of a large amount of lead elements will seriously harm the environment and human health, and the development of lead-free ceramic capacitors has become an inevitable trend. Lead-free energy storage ceramics often have the advantages of high power density, ultra-fast charging and discharging speed, stable matrix and strong environmental adaptability, but their low energy storage density and energy storage efficiency seriously limit the development of devices in the direction of high-end, miniaturization, intelligence and integration.

[0003] In lead-free energy storage ceramics, the strontium titanate system has attracted attention in the field of dielectric energy storage due to its high spontaneous polarization strength. However, due to its large remnant polarization strength and low breakdown field strength, the energy storage efficiency and energy storage density are low, which restricts its application possibilities. In view of this, at present, strontium titanate solid solutions are mainly synthesized by doping other chemical components, but the effects of the strontium titanate solid solutions of various components in the prior art are limited. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a strontium titanate-based relaxor ferroelectric ceramic material with high energy storage density and efficiency and a preparation method thereof, which reduces the remnant polarization strength and improves the breakdown field strength while retaining the high polarization strength, thereby improving the energy storage density and energy storage efficiency, so that it can better meet the needs of practical applications.

[0005] To solve the above technical problems, the present application provides the following technical solutions:

[0006] In a first aspect, the present application provides a strontium titanate-based relaxor ferroelectric ceramic material with high energy storage density and efficiency, which has a chemical composition of (1-x)(0.5SrTiO3-0.5Bi 0.5 Na 0.5 TiO3)-xBaHfO3, x = 0.01-0.3.

[0007] Preferably, x = 0.1-0.3.

[0008] Further preferably, x = 0.3. In the above preferred x scheme, the ceramic can withstand an electric field strength of 680 kV / cm, and its effective energy storage density is 12.4 J / cm 3 at this electric field, and the energy storage efficiency is 91.8 %.

[0009] In a second aspect, the present application provides a preparation method of a strontium titanate-based relaxor ferroelectric ceramic material with high energy storage density and efficiency, comprising the following steps:

[0010] S1: the chemical composition of the strontium titanate-based relaxor ferroelectric ceramic material with high energy storage density and efficiency according to the first aspect is (1-x)(0.5SrTiO3-0.5Bi 0.5 Na 0.5 TiO3)-xBaHfO3 stoichiometric ratio, raw materials Bi2O3, Na2CO3, TiO2, SrCO3, BaCO3, and HfO2 are weighed, mixed with anhydrous ethanol, ball milled, then dried, ground, once calcined, and cooled;

[0011] S2: a binder is added dropwise to the powder sample obtained in S1 for grinding and granulation, then the binder is removed after molding, and then sintering.

[0012] Preferably, the ball milling time in S1 is 8-10 h, and the ball milling speed is 200-400 r / min.

[0013] Preferably, the once calcination conditions in S1 include a temperature of 800-900℃ and a time of 1-3 h.

[0014] Preferably, the binder in S2 is PVA. Further preferably, the binder is introduced in the form of a solution, and the mass concentration of PVA in the solution is 5-8 wt%. Preferably, the solvent in the binder solution is deionized water.

[0015] Preferably, the molding in S2 is tabletting, and the pressure used in the tabletting process is 5-7 Mpa.

[0016] Preferably, the binder removal conditions in S2 include a temperature of 500-600℃ and a time of 1-3 h.

[0017] Preferably, the sintering conditions in S2 include a temperature of 1200-1300℃ and a time of 1-3 h.

[0018] The beneficial effects of the above technical solutions of the present application are as follows:

[0019] By introducing an appropriate amount of BaHfO3 into the specific substrate of SrTiO3 and Bi 0.5 Na 0.5 TiO3 with a specific ratio, the remanent polarization and the breakdown field strength can be reduced while retaining the high polarization strength, thereby improving the energy storage density and efficiency, so that it can better meet the needs of practical applications. The main reason is that the appropriate amount of BaHfO3 component in the introduced Ba 2+due to the suitable difference in the chemical valence or size of the A-site ion (i.e., Sr 2+ , Bi 3+ , Na + ) in the crystal structure, the suitable difference in the size of Hf 4+ and the B-site ion (i.e., Ti 4+ ), and the large ionic radius of Ba 2+ which can increase the disorder degree of the A-site ion, favoring the conversion of the ordered macroscopic ferroelectric domain into the disordered nanodomain cluster, reducing the polarization hysteresis and thus improving the energy storage efficiency; and the specific proportion of SrTiO3 and Bi 0.5 Na 0.5 TiO3, which can appropriately increase the disorder degree of the A-site ion of the matrix crystal, further favoring the doping and solid solution of Ba 2+ , improving the ion disorder degree and thus reducing the polarization hysteresis. Meanwhile, the grain size of the component is small, and the sample resistance is large, so that the breakdown field strength is improved, thereby improving the effective energy storage density and energy storage efficiency. Among them, the value range of x is appropriate, which is conducive to reasonably controlling the doping amount, maintaining the stability of the crystal lattice while increasing the ion disorder degree, so that the material system composition is near the relaxor phase to obtain high energy storage performance. If x is too large, the lattice distortion is serious, the system composition deviates from the relaxor phase, and the purpose of improving the energy storage performance cannot be achieved.

[0020] The preparation method of the present application can obtain strontium titanate-based relaxor ferroelectric ceramics with high energy storage density and efficiency, wherein the 0.7 (0.5SrTiO3-0.5Bi 0.5 Na 0.5 TiO3)-0.3BaHfO3 relaxor ferroelectric ceramic has a breakdown field strength of 680 kV / cm in a specific embodiment, which is higher than most strontium titanate-based energy storage ceramics, and an effective energy storage density of 12.4 J / cm 3 and an energy storage efficiency of 91.8%.

[0021] In addition, the strontium titanate-based relaxor ferroelectric ceramic of the present application also exhibits excellent environmental stability, with an effective energy storage density of 5.35 ± 0.3 J / cm 3 at 40-150℃, an effective energy storage density of 5.54 ± 0.05 J / cm 3 at 1-100 Hz test conditions, and an effective energy storage density of 5.58 ± 0.03 J / cm 1 at 10 8 -10 3 cycle times. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 XRD patterns of the strontium titanate-based relaxor ferroelectric ceramics prepared in Comparative Example 1 and Examples 1-3;

[0023] Figure 2 SEM image of the strontium titanate-based relaxor ferroelectric ceramic prepared in Example 1;

[0024] Figure 3 Unipolar P-E curve of the strontium titanate-based relaxor ferroelectric ceramic prepared in Example 1 under different electric field strengths;

[0025] Figure 4 Curve of the energy storage property of the strontium titanate-based relaxor ferroelectric ceramic prepared in Example 1 as a function of electric field strength;

[0026] Figure 5 Unipolar P-E curve of the strontium titanate-based relaxor ferroelectric ceramic prepared in Example 1 under a temperature gradient of 40-150 °C;

[0027] Figure 6 Unipolar P-E curve of the strontium titanate-based relaxor ferroelectric ceramic prepared in Example 1 under a test frequency of 1-100 Hz;

[0028] Figure 7 Unipolar P-E curve of the strontium titanate-based relaxor ferroelectric ceramic prepared in Example 1 under 10 1 -10 8 cycles. DETAILED DESCRIPTION

[0029] To make the technical problems to be solved by the present application, technical solutions and advantages clearer, the following will be described in detail in conjunction with the drawings and specific examples. In the following examples, the PVA binder meets the following requirements: introduced in the form of a solution, the solvent is deionized water, and the mass concentration of PVA in the solution is 5 wt%.

[0030] Comparative Example 1:

[0031] 0.5SrTiO3-0.5Bi 0.5 Na 0.5TiO3 ferroelectric ceramic. 5.8833 grams of Bi2O3, 1.3275 grams of Na2CO3, 8.1500 grams of TiO2, 7.4561 grams of SrCO3 are weighed according to the chemical dosage ratio, and the weighing error is between ±0.0005 grams. Pour the weighed raw materials into a ball mill tank, add anhydrous ethanol for ball milling for 10 hours at a speed of 300 r / min, and then sequentially perform drying and grinding treatment on the ball-milled sample. Then, the uniformly mixed powder is placed in a crucible, covered, and placed in a muffle furnace set at a temperature of 830 ℃ for calcination for 2 hours. After cooling, the sample is placed in a mortar, an appropriate amount of PVA binder is added, and the sample is ground and granulated. After uniform grinding, the sample is poured into a φ = 10 mm mold and pressed into a sheet using a cold isostatic press. The sheet is then placed in a muffle furnace for degassing and sintering. The degassing conditions are 550 ℃ for 2 hours, and the sintering conditions are 1220 ℃ for 2 hours. A strontium titanate ferroelectric ceramic material is obtained. After cooling, the thickness of the ceramic sheet is polished to 40-50 μm, and gold plating electrodes are sprayed on the upper and lower surfaces for energy storage performance testing (the same as the subsequent examples).

[0032] In this example, the maximum applied electric field strength is 80 kV / cm, at which the total energy storage density is 1.97 J / cm 3 , the effective energy storage density reaches 0.59 J / cm 3 , and the energy storage efficiency reaches 29.9 %.

[0033] Example 1:

[0034] A 0.7(0.5SrTiO3-0.5Bi 0.5 Na 0.5 TiO3)-0.3BaHfO3 ferroelectric ceramic is prepared using the present application. 4.1183 grams of Bi2O3, 0.9293 grams of Na2CO3, 5.7050 grams of TiO2, 5.2192 grams of SrCO3, 5.9800 grams of BaCO3, and 6.4436 grams of HfO2 are weighed according to the chemical dosage ratio, and the weighing error is between ±0.0005 grams. Pour the weighed raw materials into a ball mill tank, add anhydrous ethanol for ball milling for 10 hours at a speed of 300 r / min, and then sequentially perform drying and grinding treatment on the ball-milled sample. Then, the uniformly mixed powder is placed in a crucible, covered, and placed in a muffle furnace set at a temperature of 830 ℃ for calcination for 2 hours. After cooling, the sample is placed in a mortar, an appropriate amount of PVA binder is added, and the sample is ground and granulated. After uniform grinding, the sample is poured into a φ = 10 mm mold and pressed into a sheet using a cold isostatic press. The sheet is then placed in a muffle furnace for degassing and sintering. The degassing conditions are 550 ℃ for 2 hours, and the sintering conditions are 1220 ℃ for 2 hours. A strontium titanate ferroelectric ceramic material is obtained. After cooling, the thickness of the ceramic sheet is polished to 40-50 μm, and gold plating electrodes are sprayed on the upper and lower surfaces for energy storage performance testing (the same as the subsequent examples).

[0035] Example 2:

[0036] Reference is made to Example 1, except that 0.9 (0.5SrTiO3-0.5Bi 0.5 Na 0.5 TiO3)-0.1BaHfO3 ferroelectric ceramic is prepared by using the present application. 5.2950 grams of Bi2O3, 1.1948 grams of Na2CO3, 7.3350 grams of TiO2, 6.7105 grams of SrCO3, 1.9933 grams of BaCO3, and 2.148 grams of HfO2 are weighed according to the chemical dosage ratio, with a weighing error of ±0.0005 grams.

[0037] In this example, the maximum electric field strength that can be applied is 360 kV / cm, at which time the total energy storage density is 5.81 J / cm 3 , the effective energy storage density reaches 3.27 J / cm 3 , and the energy storage efficiency is as high as 56.3%.

[0038] Example 3:

[0039] Reference is made to Example 1, except that 0.9 (0.5SrTiO3-0.5Bi 0.5 Na 0.5 TiO3)-0.1BaHfO3 ferroelectric ceramic is prepared by using the present application. 5.2950 grams of Bi2O3, 1.1948 grams of Na2CO3, 7.3350 grams of TiO2, 6.7105 grams of SrCO3, 1.9933 grams of BaCO3, and 2.148 grams of HfO2 are weighed according to the chemical dosage ratio, with a weighing error of ±0.0005 grams.

[0040] In this example, the maximum electric field strength that can be applied is 360 kV / cm, at which time the total energy storage density is 5.81 J / cm 3 , the effective energy storage density reaches 3.27 J / cm 3 , and the energy storage efficiency is as high as 56.3%.

[0041] Figure 1 The XRD pattern of the strontium titanate-based relaxor ferroelectric ceramic powder prepared for Comparative Example 1 and Examples 1-3 is shown in the figure. As can be seen from the figure, the prepared series of strontium titanate-based relaxor ferroelectric ceramic samples all have a single cubic perovskite structure, and no obvious impurity phase is observed, indicating that the new component BaHfO3 has been successfully solid-solved into the lattice of the matrix to form a uniform solid solution.

[0042] Figure 2 The SEM pattern of the strontium titanate-based relaxor ferroelectric ceramic prepared for Example 1 is shown in the figure. As can be seen from the figure, the grain size of the ceramic is about 1.21 μm, and the density is high, which is conducive to improving the breakdown field strength of the sample.

[0043] Figure 3 The monopolar hysteresis loops of the 40-50 μm thick strontium titanate-based relaxor ferroelectric ceramic prepared in Example 1 under different electric fields can be seen from the figure. The ceramic hysteresis loops are slender, and the remanent polarization thereof is small, and the saturation polarization gradually increases, and the maximum electric field strength can reach 680 kV / cm.

[0044] Figure 4 The curve of the energy storage characteristics of the strontium titanate-based relaxor ferroelectric ceramic prepared in Example 1 with the electric field strength can be seen. The maximum electric field strength that can be applied is 680 kV / cm, at which the total energy storage density is 13.6 J / cm 3 , the effective energy storage density reaches 12.4 J / cm 3 , and the energy storage efficiency is as high as 91.8 %.

[0045] Comparative Example 2

[0046] Reference is made to Example 1, except that 0.7 (0.3 SrTiO3-0.7 Bi 0.5 Na 0.5 TiO3)-0.3 BaHfO3 ferroelectric ceramic is prepared by using the application. 2.5945 grams of Bi2O3, 0.5945 grams of Na2CO3, 2.5412 grams of TiO2, 1.4092 grams of SrCO3, 2.6910 grams of BaCO3, and 2.8703 grams of HfO2 are weighed according to the chemical dosage ratio, and the weighing error is between ±0.0005 grams.

[0047] In this example, the maximum electric field strength that can be applied is 65 kV / cm, at which the total energy storage density is 0.88 J / cm 3 , the effective energy storage density reaches 0.65 J / cm 3 , and the energy storage efficiency is 73.6 %.

[0048] Test Example

[0049] The environmental stability of the product obtained is tested by taking Example 1 as an example.

[0050] Figure 5 The monopolar hysteresis loops of the 40-50 μm thick strontium titanate-based relaxor ferroelectric ceramic sample prepared in Example 1 under a temperature gradient of 40-150 °C, and the test electric field is 400 kV / cm. Under this test condition, the effective energy storage density thereof is 5.35±0.3 J / cm 3 , and it can be seen that the effective energy storage density of the sample has temperature stability.

[0051] Figure 6The unipolar hysteresis loops of the 40-50 μm thick strontium titanate-based relaxor ferroelectric ceramic sample prepared in Example 1 were measured at room temperature and at an electric field strength of 400 kV / cm from different test frequencies, the test frequencies being 1-100 Hz. Its effective energy storage density was 5.54 ± 0.05 J / cm 3 It can be seen that the effective energy storage density of the sample has good frequency stability.

[0052] Figure 7 The unipolar hysteresis loops of the 40-50 μm thick strontium titanate-based relaxor ferroelectric ceramic sample prepared in Example 1 were measured at room temperature and at an electric field strength of 400 kV / cm from different cycle numbers, the cycle numbers being 10 1 -10 8 Its effective energy storage density was 5.58 ± 0.03 J / cm 3 It can be seen that the effective energy storage density of the sample has good cycle stability.

[0053] The above is the preferred embodiment of the present application, it should be noted that for those skilled in the art, without departing from the principles of the present application, can also make a number of improvements and refinements, these improvements and refinements should also be considered within the scope of the present application.

Claims

1. A strontium titanate-based ferroelectric ceramic material having both high energy storage density and efficiency, characterized by, having a chemical composition of (1-x)(0.5SrTiO3-0.5Bi 0.5 Na 0.5 TiO3)-xBaHfO3, x = 0.

3.

2. A method for preparing a strontium titanate-based ferroelectric ceramic material with high energy storage density and efficiency, characterized in that, The method comprises the following steps: S1: The chemical composition of the strontium titanate-based relaxor ferroelectric ceramic material with high energy storage density and efficiency according to claim 1 is (1-x)(0.5SrTiO3-0.5Bi 0.5 Na 0.5 TiO3)-xBaHfO3 stoichiometric ratio, the raw materials Bi2O3, Na2CO3, TiO2, SrCO3, BaCO3, HfO2 are weighed, mixed with anhydrous ethanol, ball milled, then dried, ground, once calcined and cooled; S2: adding a binder to the powder sample obtained in S1 to perform milling and granulation, then performing de-binding and sintering in sequence after molding.

3. The method for preparing strontium titanate-based ferroelectric ceramic material with high energy storage density and efficiency according to claim 2, characterized in that, The milling time in S1 is 8-10 h, and the milling speed is 200-400 r / min.

4. The method for preparing strontium titanate-based ferroelectric ceramic material with high energy storage density and efficiency according to claim 2, characterized in that, The conditions of the first calcination in S1 include a temperature of 800-900 ℃ and a time of 1-3 h.

5. The method for preparing strontium titanate-based ferroelectric ceramic material with high energy storage density and efficiency according to claim 2, characterized in that, The binder in S2 is PVA, which is introduced in the form of a solution, and the mass concentration of PVA in the solution is 5-8 wt%.

6. The method for preparing strontium titanate-based ferroelectric ceramic material with high energy storage density and efficiency according to claim 2, characterized in that, The molding in S2 is tabletting, and the pressure used in the tabletting process is 5-7 MPa.

7. The method for preparing strontium titanate-based ferroelectric ceramic material with high energy storage density and efficiency according to claim 2, characterized in that, The de-binding conditions in S2 include a temperature of 500-600 ℃ and a time of 1-3 h.

8. The method for preparing strontium titanate-based ferroelectric ceramic material with high energy storage density and efficiency according to claim 2, characterized in that, The sintering conditions in S2 include a temperature of 1200-1300 ℃ and a time of 1-3 h.

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