A sodium bismuth titanate-strontium titanate high-energy storage lead-free ceramic material and its preparation method

Abstract

The present invention relates to the technical field of ceramic materials, and discloses a sodium bismuth titanate-strontium titanate high-energy storage lead-free ceramic material. The nominal chemical formula of this material is 50 mol% Na 0.5 Bi 0.5 TiO3 - 50 mol% SrTiO3 - x wt% Nb2O5 - y wt% Sm2O3 - z wt% HfO2. Where 1 < x < 2, 0.8 < y < 1.2, 3 < z < 4.8. The preparation method is as follows: After proportioning according to the stoichiometric ratio of the above formula, use anhydrous ethanol as the ball-milling medium, ball-mill and mix evenly, and then dry; add PVA binder, granulate, press, and degrease to obtain a ceramic green body; under the conditions of an electric field strength of 280 - 380 V / cm and a current strength of 2.5 - 3.5 A / cm 2 Perform flash sintering treatment, sinter at 650 - 750 °C for 100 - 400 s to obtain a ceramic block material. The preparation process of the present invention is novel, relatively low in cost, does not contain lead elements, is environmentally friendly, has a high energy storage density and a fast charge-discharge speed, and has strong thermal stability, showing good industrialization prospects in the field of dielectric energy storage ceramics.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic materials, and particularly to a sodium bismuth titanate-strontium titanate high-energy storage lead-free ceramic material and a preparation method thereof. Background Art

[0002] In recent years, dielectric energy storage capacitors have received increasing attention due to their characteristics such as high power density and extremely fast charge and discharge speeds. Compared with batteries and supercapacitors, they show great advantages in pulsed power system applications. Among many dielectric energy storage capacitor materials, ceramic-based dielectric energy storage capacitors have received extensive attention due to their relatively high dielectric constant, moderate breakdown field strength, excellent thermal stability, superior mechanical strength, and low cost.

[0003] As is well known, sodium bismuth titanate-based ceramics, as a perovskite-type ferroelectric, have attracted much attention due to their excellent piezoelectric properties. However, sodium bismuth titanate-based ceramics have significant disadvantages such as poor sintering density, many types of defects, and low breakdown electric field strength due to the easy volatilization of Na and Bi elements. And the most important is that the relatively large remanent polarization intensity results in poor dielectric energy storage performance. In recent years, obtaining lead-free sodium bismuth titanate-based ceramics with high energy storage characteristics through doping modification and optimizing preparation conditions has become a research hotspot in the current energy storage material technology direction. The present application proposes a sodium bismuth titanate-strontium titanate high-energy storage lead-free ceramic material and a preparation method thereof based on the existing technology. Summary of the Invention

[0004] The present invention provides a sodium bismuth titanate-strontium titanate high-energy storage lead-free ceramic material and a preparation method thereof, which solve the problems raised in the above background art.

[0005] The present invention provides the following technical solutions: A sodium bismuth titanate-strontium titanate high-energy storage lead-free ceramic material, the nominal chemical formula of the material is 50 mol% Na 0.5 Bi 0.5 TiO3 - 50 mol% SrTiO3 - x wt% Nb2O5 - y wt% Sm2O3 - z wt% HfO2, where 1 < x < 2, 0.8 < y < 1.2, 3 < z < 4.8.

[0006] A preparation method of a sodium bismuth titanate-strontium titanate high-energy storage lead-free ceramic material, the specific steps are as follows:

[0007] (1) Using anhydrous sodium carbonate, bismuth trioxide, titanium dioxide, and strontium carbonate as starting materials, according to Na 0.5 Bi 0.5Ingredients are prepared according to the molar ratio of TiO3:SrTiO3 = (0.97 - 1.03):(1.03 - 0.97), and then niobium pentoxide, samarium sesquioxide, and hafnium dioxide are added in mass percentages of 1 - 2, 0.8 - 1.2, and 3 - 4.8 respectively. Then, using absolute ethanol as the ball-milling medium, after ball-milling and mixing evenly, it is dried;

[0008] (2) The pre-fired powder prepared in step (1) is pulverized, and then using absolute ethanol as the ball-milling medium, it is ball-milled, mixed evenly, dried, and ground into a micron-sized powder;

[0009] (3) The powder prepared in step (2) is added with a PVA binder. The mass ratio of the powder prepared in step (2) to the PVA binder is 95:5, and then through granulation, tabletting, and debinding, a ceramic green body is obtained;

[0010] (4) The ceramic green body prepared in step (3) is subjected to flash sintering under the conditions of an electric field strength of 28 - 38 V / mm and a current density of 2.5 - 3.5 A / cm 2 and sintered at a temperature of 650 - 750 °C for 100 - 400 s, thus obtaining the lead-free sodium bismuth titanate-strontium titanate ceramic material.

[0011] Optionally, the purity of all starting raw material powders in step (1) is 99.99%.

[0012] Optionally, in step (1), the ball-milling time is 16 - 18 h, the drying temperature is 100 - 110 °C, and the drying time is 17 - 19 h.

[0013] Optionally, in step (3), the diameter of the tabletting mold is 6 - 8 mm, the pressure is 90 - 120 MPa, and the pressure holding time is 3 - 6 minutes.

[0014] Optionally, in step (3), the debinding temperature is 520 - 560 °C, and the debinding time is 2 - 3.5 h.

[0015] Optionally, in step (4), the electric field strength of the flash sintering is 280 - 380 V / cm, and the current density is 2.5 - 3.5 A / cm 2 .

[0016] Optionally, in step (4), the firing temperature of the flash sintering is 650 - 750 °C, and the heat preservation time is 100 - 400 s.

[0017] The present invention has the following beneficial effects:

[0018] The preparation process of the present invention is novel, with relatively low cost, does not contain lead elements, is environmentally friendly, has a high energy storage density and a fast charge and discharge speed, has strong thermal stability, and has good industrialization prospects in the field of dielectric energy storage ceramics. Description of the Drawings

[0019] Figure 1 50 mol% Na prepared in the embodiment of the present invention 0.5 Bi 0.5 TiO3 - 50 mol% SrTiO3 - 1.2 wt% Nb2O5 - 0.95 wt% Sm2O3 - 3.6 wt% HfO2, X-ray pattern of the sodium bismuth titanate-strontium titanate-based lead-free ceramic material with high energy storage characteristics

[0020] Figure 2 50 mol% Na prepared in the embodiment of the present invention 0.5 Bi 0.5 TiO3 - 50 mol% SrTiO3 - 1.2 wt% Nb2O5 - 0.95 wt% Sm2O3 - 3.6 wt% HfO2, micrograph of the sodium bismuth titanate-strontium titanate-based lead-free ceramic material with high energy storage characteristics

[0021] Figure 3 50 mol% Na prepared in the embodiment of the present invention 0.5 Bi 0.5 TiO3 - 50 mol% SrTiO3 - 1.2 wt% Nb2O5 - 0.95 wt% Sm2O3 - 3.6 wt% HfO2, Weibull distribution fitting diagram of the breakdown electric field strength of the sodium bismuth titanate-strontium titanate-based lead-free ceramic material with high energy storage characteristics

[0022] Figure 4 50 mol% Na prepared in the embodiment of the present invention 0.5 Bi 0.5 TiO3 - 50 mol% SrTiO3 - 1.2 wt% Nb2O5 - 0.95 wt% Sm2O3 - 3.6 wt% HfO2, electric hysteresis loop diagram of the sodium bismuth titanate-strontium titanate-based lead-free ceramic material with high energy storage characteristics

[0023] Figure 5 50 mol% Na prepared in the embodiment of the present invention 0.5 Bi 0.5 TiO3 - 50 mol% SrTiO3 - 1.2 wt% Nb2O5 - 0.95 wt% Sm2O3 - 3.6 wt% HfO2, electric hysteresis loop diagram of the temperature-variable test of the sodium bismuth titanate-strontium titanate-based lead-free ceramic material with high energy storage characteristics

[0024] Figure 6 50 mol% Na prepared in the embodiment of the present invention 0.5 Bi 0.5Current curves of 50mol% NaBiTiO3-50mol% SrTiO3-1.2wt% Nb2O5-0.95wt% Sm2O3-3.6wt% HfO2 lead-free ceramic material with high energy storage characteristics under different electric field strengths at room temperature in the underdamped state;

[0025] Figure 7 50mol% Na 0.5 Bi 0.5 Current curves of 50mol% NaBiTiO3-50mol% SrTiO3-1.2wt% Nb2O5-0.95wt% Sm2O3-3.6wt% HfO2 lead-free ceramic material with high energy storage characteristics during variable temperature testing in the underdamped state;

[0026] Figure 8 50mol% Na 0.5 Bi 0.5 Current curves of 50mol% NaBiTiO3-50mol% SrTiO3-1.2wt% Nb2O5-0.95wt% Sm2O3-3.6wt% HfO2 lead-free ceramic material with high energy storage characteristics under different electric field strengths at room temperature in the overdamped state;

[0027] Figure 9 50mol% Na 0.5 Bi 0.5 Current curves of 50mol% NaBiTiO3-50mol% SrTiO3-1.2wt% Nb2O5-0.95wt% Sm2O3-3.6wt% HfO2 lead-free ceramic material with high energy storage characteristics during variable temperature testing in the overdamped state. Detailed implementation manners

[0028] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0029] The present invention provides a preparation method for a sodium bismuth titanate-strontium titanate high energy storage lead-free ceramic material, and the specific steps are as follows:

[0030] (1) Raw materials of anhydrous sodium carbonate, bismuth trioxide, titanium dioxide, strontium carbonate, niobium pentoxide, samarium trioxide, and hafnium dioxide with a purity of 99.99% are in a chemical stoichiometric ratio of 50mol% Na 0.5 Bi 0.5The TiO3-50mol% SrTiO3-1.2wt% Nb2O5-0.95wt% Sm2O3-3.6wt% HfO2 batch is placed in a nylon ball milling tank. Zirconia balls and absolute ethanol are selected as the ball milling media. The mixing ball milling time is 16 - 18 h, and the rotation speed is 350 - 380 revolutions per minute. The product obtained after ball milling is placed in an oven at 100 - 110 °C and dried for 17 - 19 h.

[0031] (2) Take out the dried powder and grind it thoroughly. Add 5 - 10 g of the taken-out powder into 4 - 10 mL of PVA solution and grind it thoroughly. The concentration of PVA is 6 - 8 wt%; Take 0.3 - 0.4 g of the thoroughly ground powder and place it in a mold with a diameter of 6 - 10 mm, and keep the pressure at 90 - 120 MPa for 3 - 6 minutes. After pressing, the green body is degreased at 520 - 560 °C for 2 - 3.5 h.

[0032] (3) The ceramic green body obtained after degreasing is subjected to flash sintering treatment under the conditions of an electric field strength of 280 - 380 V / cm and a current density of 2.5 - 3.5 A / cm 2 and sintered at 650 - 750 °C for 100 - 400 s to obtain the corresponding ceramic bulk material.

[0033] The sodium bismuth titanate-strontium titanate-based lead-free ceramic material prepared according to the above method is characterized for its phase structure and microstructure, as shown in Appendix Figure 1 and Appendix Figure 2 . It can be seen that the ceramic material obtained by the above preparation method exists in a single-phase perovskite structure and has a microstructure with fine and uniformly distributed grains. In addition, through multiple electric breakdown experiments on it, and using the Weibull distribution to determine its reliable breakdown field strength value, as shown in Appendix Figure 3 . And according to the experimental results obtained above, the P-E curve is tested at this electric field strength, as shown in Appendix Figure 4 . For this sodium bismuth titanate-strontium titanate-based lead-free ceramic material, at an electric field strength of 40 kV / mm, its effective energy storage density can reach a relatively high value of 7.78 J / cm 3 , and maintain a relatively high energy storage efficiency value of 79.5%. In addition, in the temperature range of 20 °C - 120 °C, this sample also has excellent energy storage stability, as shown in Appendix Figure 5 . Moreover, this sample also has a relatively high power density of 119 MW / cm 3 , and a relatively fast charge-discharge speed of 117 ns, as shown in Appendix Figure 6 and Appendix Figure 7 . Refer to Appendix Figure 8 and Appendix Figure 9, The above excellent charge-discharge characteristics have high temperature stability (in the temperature range of 20°C to 120°C), meet the actual application requirements of ceramic energy storage capacitors, and are expected to be applied in the electronic ceramic market.

[0034] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A sodium bismuth titanate-strontium titanate high energy storage lead-free ceramic material, characterized in that: The chemical formula of the material is 50 mol% Na 0.5 Bi 0.5 TiO3 - 50 mol% SrTiO3 - x wt% Nb2O5 - y wt% Sm2O3 - z wt% HfO2, where 1 < x < 2, 0.8 < y < 1.2, 3 < z < 4.

8.

2. A preparation method of a sodium bismuth titanate-strontium titanate high energy storage lead-free ceramic material as described in claim 1, characterized in that: The specific steps are as follows: (1) Put raw materials of anhydrous sodium carbonate, bismuth trioxide, titanium dioxide, strontium carbonate, niobium pentoxide, samarium sesquioxide, and hafnium dioxide with a purity of 99.99% into a nylon ball milling tank according to the chemical stoichiometric ratio of 50 mol% Na 0.5 Bi 0.5 TiO3 - 50 mol% SrTiO3 - 1.2wt% Nb2O5 - 0.95wt% Sm2O3 - 3.6wt% HfO2 for batching. Select zirconia balls and absolute ethanol as ball milling media. The mixing ball milling time is 16 - 18 h, and the rotation speed is 350 - 380 revolutions per minute. Place the product obtained after ball milling in an oven at 100 - 110 °C and dry it for 17 - 19 h; (2) Take out the dried powder and grind it sufficiently. Add 5 - 10 g of the taken-out powder into 4 - 10 mL of PVA solution and grind it sufficiently. The concentration of PVA is 6 - 8 wt%. Take 0.3 - 0.4 g of the sufficiently ground powder and place it in a mold with a diameter of 6 - 10 mm, keep the pressure at 90 - 120 MPa for 3 - 6 minutes. After pressing, the green body is calcined at 520 - 560 °C for 2 - 3.5 h; (3)The ceramic green body obtained after debinding is subjected to flash sintering under the conditions of an electric field strength of 280 - 380 V / cm and a current strength of 2.5 - 3.5 A / cm 2 and sintered at 650 - 750 °C for 100 - 400 s to obtain the corresponding ceramic bulk material.

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