A lead-free high-dielectric-constant ultra-low-loss dielectric material for high-voltage ceramic capacitors

Abstract

This invention discloses a lead-free, high-dielectric-constant, ultra-low-loss dielectric material for high-voltage ceramic capacitors, relating to the field of dielectric material technology. It comprises the following raw materials in molar amounts: Bi₂Ti₂O₇ 4.6-8.7 parts, Nb₂O₅ 0.04-0.13 parts, Cr₂O₃ 0.1-0.4 parts, Fe₂O₃ 0.1-0.4 parts, Dy₂O₃ 0.05-0.1 parts, BaTiO₃ 61-69 parts, and SrTiO₃ 31-39 parts. This lead-free, high-dielectric-constant, ultra-low-loss dielectric material for high-voltage ceramic capacitors exhibits high dielectric constant, ultra-low dielectric loss, high breakdown field strength, and temperature characteristics meeting the Z5T standard.

Description

Technical Field

[0001] This invention relates to the field of dielectric materials technology, and in particular to a lead-free, high dielectric constant, ultra-low loss dielectric material for high voltage ceramic capacitors. Background Technology

[0002] As electronic devices evolve towards miniaturization and higher performance, the performance requirements for high-voltage ceramic capacitors are increasing. High-voltage ceramic capacitors are indispensable components in electronic circuits, widely used in power electronics, communications, aerospace, and other fields. Their performance directly affects the stability and reliability of the entire circuit system. The performance of high-voltage ceramic capacitors, in turn, depends on the dielectric material. Therefore, developing a high-dielectric-constant, ultra-low-loss dielectric material for high-voltage ceramic capacitors is of paramount importance.

[0003] Among existing high-voltage ceramic capacitor dielectric materials, traditional lead-containing dielectric materials, while possessing good dielectric properties, pose serious threats to the environment and human health due to the toxicity of lead. Against the backdrop of increasing global environmental awareness, lead-free technology has become an inevitable trend in the development of high-voltage ceramic capacitor dielectric materials. On the other hand, the dielectric constant of current high-voltage ceramic capacitor dielectric materials is not high in the ultra-low loss field, generally around 2000. If the dielectric constant of existing high-voltage ceramic capacitors is to be increased to around 3000, the minimum loss can only be controlled to 0.2%, far from meeting the requirements of the ultra-low loss field.

[0004] For example, Chinese invention patent CN101774802B discloses a ceramic dielectric material composed of the following components by molar percentage: BaCO3 12.50–34.50%, SrCO3 14.79–37.49%, TiO2 45.29–49.39%, CeO2 0.01–0.99%, Dy2O3 0.02–0.89%, and MnO2 0.01–0.14%. The purpose of this invention is to overcome the shortcomings of existing technologies and provide a dielectric ceramic material with high dielectric constant and low loss. Another objective is to provide a method for preparing this dielectric ceramic material. This invention adjusts the ratio of Ba and Sr in the basic formulation to lower the Curie temperature of the ceramic material below room temperature, resulting in smaller grains and high dielectric constant, low dielectric loss, and high breakdown electric field strength. However, its loss remains relatively high, making it difficult to meet the requirements for ultra-low loss applications.

[0005] It is evident that developing a lead-free high dielectric constant and ultra-low loss dielectric material for high-voltage ceramic capacitors with high dielectric constant, ultra-low dielectric loss, high breakdown field strength, and temperature characteristics meeting the Z5T standard meets market demand, has broad market value and application prospects, and is of great significance to promoting the development of dielectric materials for high-voltage ceramic capacitors. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a lead-free high dielectric constant and ultra-low loss dielectric material for high voltage ceramic capacitors with high dielectric constant, ultra-low dielectric loss, high breakdown field strength, and temperature characteristics that meet Z5T.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a lead-free high dielectric constant and ultra-low loss dielectric material for high voltage ceramic capacitors, comprising the following raw materials in molar parts: Bi2Ti2O7 4.6-8.7 parts, Nb2O5 0.04-0.13 parts, Cr2O3 0.1-0.4 parts, Fe2O3 0.1-0.4 parts, Dy2O3 0.05-0.1 parts, BaTiO3 61-69 parts, and SrTiO3 31-39 parts.

[0008] Preferably, the preparation method of Bi2Ti2O7 includes the following steps: mixing titanium dioxide powder and bismuth oxide powder evenly, adding deionized water and ball milling for 3-5 hours, drying, and keeping warm at a certain temperature for a certain time to obtain pre-synthesized Bi2Ti2O7.

[0009] Preferably, the molar ratio of the titanium dioxide powder to the bismuth oxide powder is 2:(1-1.15).

[0010] Preferably, the particle size of the titanium dioxide powder is 800-1200 mesh.

[0011] Preferably, the bismuth oxide powder has a particle size of 700-1000 mesh.

[0012] Preferably, the drying is carried out at 95-105°C for 10-15 hours.

[0013] Preferably, the specific temperature is 815-825℃.

[0014] Preferably, the specified time is 95-105 minutes.

[0015] Another object of the present invention is to provide a method for preparing the lead-free high dielectric constant ultra-low loss dielectric material for high voltage ceramic capacitors, comprising the following steps: Step S1: After mixing BaTiO3 and SrTiO3 evenly by molar amount, Bi2Ti2O7, Nb2O5, Cr2O3, Fe2O3 and Dy2O3 are added in sequence. Deionized water is added and the mixture is ball-milled for 5-7 hours. After drying, it is pressed and sintered in sequence. Step S2: Print silver electrodes on the end face and keep warm at 795-805℃ for 13-18 minutes to complete the preparation.

[0016] Preferably, the pressing pressure is 295-305 MPa.

[0017] Preferably, the sintering temperature is 1200-1280℃.

[0018] Preferably, the sintering holding time is 2-4 hours.

[0019] Due to the application of the above technical solutions, the present invention has the following beneficial effects: Through the rational selection of the dielectric material composition formula, especially the first simultaneous introduction of Cr2O3, Fe2O3, and Bi2Ti2O7, the dielectric material produced has a high dielectric constant, ultra-low dielectric loss, high breakdown field strength, and temperature characteristics meeting Z5T; through the optimization of the preparation process and composition formula, the dielectric material produced has a high dielectric constant and extremely low dielectric loss, effectively reducing energy loss and heat generation during capacitor operation, and improving capacitor efficiency and stability; after long-term testing under high-voltage conditions, the dielectric material of the present invention exhibits excellent high-voltage stability and can be reliably applied in high-voltage circuits. Detailed Implementation

[0020] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art under the premise of equivalent changes and modifications should fall within the protection scope of the present invention. Example 1

[0021] A lead-free, high-dielectric-constant, ultra-low-loss dielectric material for high-voltage ceramic capacitors is made from the following raw materials in molar parts: 4.6 parts Bi2Ti2O7, 0.04 parts Nb2O5, 0.1 parts Cr2O3, 0.1 parts Fe2O3, 0.05 parts Dy2O3, 61 parts BaTiO3, and 31 parts SrTiO3.

[0022] The preparation method of Bi2Ti2O7 includes the following steps: titanium dioxide powder and bismuth oxide powder are mixed evenly, then deionized water is added and ball-milled for 3 hours. After drying, the mixture is kept at a certain temperature for a certain time to obtain pre-synthesized Bi2Ti2O7. The molar ratio of titanium dioxide powder to bismuth oxide powder is 2:1. The particle size of titanium dioxide powder is 800 mesh. The particle size of bismuth oxide powder is 700 mesh. The drying is carried out at 95°C for 10 hours. The certain temperature is 815°C. The certain time is 95 minutes.

[0023] A method for preparing a lead-free, high-dielectric-constant, ultra-low-loss dielectric material for high-voltage ceramic capacitors includes the following steps: Step S1: After uniformly mixing BaTiO3 and SrTiO3 by molar amount, Bi2Ti2O7, Nb2O5, Cr2O3, Fe2O3 and Dy2O3 are added sequentially. Deionized water is added and the mixture is ball-milled for 5 hours. After drying, it is pressed and sintered sequentially. The pressing pressure is 295MPa; the sintering temperature is 1200℃; and the sintering holding time is 2h. Step S2: Print silver electrodes on the end face and keep warm at 795℃ for 13 minutes to complete the preparation. Example 2

[0024] A lead-free, high-dielectric-constant, ultra-low-loss dielectric material for high-voltage ceramic capacitors is made from the following raw materials in molar parts: 5.7 parts Bi2Ti2O7, 0.06 parts Nb2O5, 0.2 parts Cr2O3, 0.2 parts Fe2O3, 0.07 parts Dy2O3, 63 parts BaTiO3, and 33 parts SrTiO3.

[0025] The preparation method of Bi2Ti2O7 includes the following steps: titanium dioxide powder and bismuth oxide powder are mixed evenly, then deionized water is added and ball-milled for 3.5 hours. After drying, the mixture is kept at a certain temperature for a certain time to obtain pre-synthesized Bi2Ti2O7. The molar ratio of titanium dioxide powder to bismuth oxide powder is 2:1.05. The particle size of titanium dioxide powder is 900 mesh. The particle size of bismuth oxide powder is 800 mesh. The drying is carried out at 98°C for 12 hours. The certain temperature is 818°C. The certain time is 98 minutes.

[0026] A method for preparing a lead-free, high-dielectric-constant, ultra-low-loss dielectric material for high-voltage ceramic capacitors includes the following steps: Step S1: After uniformly mixing BaTiO3 and SrTiO3 by molar amount, Bi2Ti2O7, Nb2O5, Cr2O3, Fe2O3 and Dy2O3 are added sequentially. Deionized water is added and the mixture is ball-milled for 5-7 hours. After drying, it is pressed and sintered sequentially. The pressing pressure is 298MPa; the sintering temperature is 1230℃; and the sintering holding time is 2.5h. Step S2: Print silver electrodes on the end face and keep warm at 798℃ for 15 minutes to complete the preparation. Example 3

[0027] A lead-free, high-dielectric-constant, ultra-low-loss dielectric material for high-voltage ceramic capacitors is made from the following raw materials in molar parts: 6.6 parts Bi2Ti2O7, 0.09 parts Nb2O5, 0.25 parts Cr2O3, 0.25 parts Fe2O3, 0.08 parts Dy2O3, 66 parts BaTiO3, and 36 parts SrTiO3.

[0028] The preparation method of Bi2Ti2O7 includes the following steps: titanium dioxide powder and bismuth oxide powder are mixed evenly, then deionized water is added and ball-milled for 4 hours. After drying, the mixture is kept at a certain temperature for a certain time to obtain pre-synthesized Bi2Ti2O7. The molar ratio of titanium dioxide powder to bismuth oxide powder is 2:1.1. The particle size of titanium dioxide powder is 1000 mesh. The particle size of bismuth oxide powder is 850 mesh. The drying is carried out at 100℃ for 13 hours. The certain temperature is 820℃. The certain time is 100 minutes.

[0029] A method for preparing a lead-free, high-dielectric-constant, ultra-low-loss dielectric material for high-voltage ceramic capacitors includes the following steps: Step S1: After uniformly mixing BaTiO3 and SrTiO3 by molar amount, Bi2Ti2O7, Nb2O5, Cr2O3, Fe2O3 and Dy2O3 are added sequentially. Deionized water is added and the mixture is ball-milled for 6 hours. After drying, it is pressed and sintered sequentially. The pressing pressure is 300MPa; the sintering temperature is 1250℃; and the sintering holding time is 3h. Step S2: Print silver electrodes on the end face and keep at 800℃ for 16 minutes to complete the preparation. Example 4

[0030] A lead-free, high-dielectric-constant, ultra-low-loss dielectric material for high-voltage ceramic capacitors is made from the following raw materials in molar parts: 8.3 parts Bi2Ti2O7, 0.11 parts Nb2O5, 0.35 parts Cr2O3, 0.35 parts Fe2O3, 0.09 parts Dy2O3, 67 parts BaTiO3, and 37 parts SrTiO3.

[0031] The preparation method of Bi2Ti2O7 includes the following steps: titanium dioxide powder and bismuth oxide powder are mixed evenly, then deionized water is added and ball-milled for 4.5 hours. After drying, the mixture is kept at a certain temperature for a certain time to obtain pre-synthesized Bi2Ti2O7. The molar ratio of titanium dioxide powder to bismuth oxide powder is 2:1.13. The particle size of titanium dioxide powder is 1100 mesh. The particle size of bismuth oxide powder is 950 mesh. The drying is carried out at 103℃ for 14 hours. The certain temperature is 823℃. The certain time is 103 minutes.

[0032] A method for preparing a lead-free, high-dielectric-constant, ultra-low-loss dielectric material for high-voltage ceramic capacitors includes the following steps: Step S1: After uniformly mixing BaTiO3 and SrTiO3 by molar amount, Bi2Ti2O7, Nb2O5, Cr2O3, Fe2O3 and Dy2O3 are added sequentially. Deionized water is added and the mixture is ball-milled for 6.5 hours. After drying, it is pressed and sintered sequentially. The pressing pressure is 303 MPa; the sintering temperature is 1270℃; and the sintering holding time is 3.5 h. Step S2: Print silver electrodes on the end face and keep warm at 803℃ for 17 minutes to complete the preparation. Example 5

[0033] A lead-free, high-dielectric-constant, ultra-low-loss dielectric material for high-voltage ceramic capacitors is made from the following raw materials in molar parts: 8.7 parts Bi2Ti2O7, 0.13 parts Nb2O5, 0.4 parts Cr2O3, 0.4 parts Fe2O3, 0.1 parts Dy2O3, 69 parts BaTiO3, and 39 parts SrTiO3.

[0034] The preparation method of Bi2Ti2O7 includes the following steps: titanium dioxide powder and bismuth oxide powder are mixed evenly, then deionized water is added and ball-milled for 5 hours. After drying, the mixture is kept at a certain temperature for a certain time to obtain pre-synthesized Bi2Ti2O7. The molar ratio of titanium dioxide powder to bismuth oxide powder is 2:1.15. The particle size of titanium dioxide powder is 1200 mesh. The particle size of bismuth oxide powder is 1000 mesh. The drying is carried out at 105℃ for 15 hours. The certain temperature is 825℃. The certain time is 105 minutes.

[0035] A method for preparing a lead-free, high-dielectric-constant, ultra-low-loss dielectric material for high-voltage ceramic capacitors includes the following steps: Step S1: After uniformly mixing BaTiO3 and SrTiO3 by molar amount, Bi2Ti2O7, Nb2O5, Cr2O3, Fe2O3 and Dy2O3 are added sequentially. Deionized water is added and the mixture is ball-milled for 7 hours. After drying, it is pressed and sintered sequentially. The pressing pressure is 305MPa; the sintering temperature is 1280℃; and the sintering holding time is 4h. Step S2: Print silver electrodes on the end face and keep warm at 805℃ for 18 minutes to complete the preparation.

[0036] Comparative Example 1 A lead-free, high dielectric constant, and ultra-low loss dielectric material for high-voltage ceramic capacitors is basically the same as that in Example 1, except that Bi2Ti2O7 is not added.

[0037] Comparative Example 2 A lead-free, high dielectric constant, and ultra-low loss dielectric material for high-voltage ceramic capacitors is basically the same as that in Example 1, except that Cr2O3 and Fe2O3 are not added.

[0038] To further illustrate the beneficial technical effects of the lead-free high dielectric constant and ultra-low loss dielectric materials for high-voltage ceramic capacitors involved in the various embodiments of the present invention, the dielectric properties of the lead-free high dielectric constant and ultra-low loss dielectric materials for high-voltage ceramic capacitors involved in Examples 1-5 and Comparative Examples 1-2 were tested using an Agilent 4294A precision impedance analyzer and an E4980A LCR meter, respectively. The electric field strength Eb value was obtained by applying a high voltage DC voltage to the ceramic sample in silicone oil at room temperature using a Keithley 2410 digital source meter for IV testing. The test results are shown in Table 1.

[0039] As can be seen from Table 1, the lead-free high dielectric constant and ultra-low loss dielectric materials for high voltage ceramic capacitors involved in the embodiments of the present invention have a larger dielectric constant, ultra-low dielectric loss, and higher electric field strength than the comparative products; the combined use of Bi2Ti2O7, Cr2O3 and Fe2O3 has a beneficial effect on improving the above performance.

[0040] Meanwhile, the temperature coefficient of the capacitor was tested within a temperature range of -55℃ to +125℃. The test results showed that the dielectric materials of each example met the temperature characteristics of Z5T and were suitable for most normal use scenarios.

[0041] Table 1. Performance Test Results of Lead-Free High-Dielectric-Constant Ultra-Low-Loss Dielectric Materials for High-Voltage Ceramic Capacitors The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A lead-free, high-dielectric-constant, ultra-low-loss dielectric material for high-voltage ceramic capacitors, characterized in that... It is made from the following raw materials measured in molar parts: Bi2Ti2O7 4.6-8.7 parts, Nb2O5 0.04-0.13 parts, Cr2O3 0.1-0.4 parts, Fe2O3 0.1-0.4 parts, Dy2O3 0.05-0.1 parts, BaTiO3 61-69 parts, and SrTiO3 31-39 parts.

2. The lead-free, high-dielectric-constant, ultra-low-loss dielectric material for high-voltage ceramic capacitors according to claim 1, characterized in that, The preparation method of Bi2Ti2O7 includes the following steps: titanium dioxide powder and bismuth oxide powder are mixed evenly, then deionized water is added and ball-milled for 3-5 hours. After drying, the mixture is kept at a certain temperature for a certain time to obtain pre-synthesized Bi2Ti2O7.

3. The lead-free, high-dielectric-constant, ultra-low-loss dielectric material for high-voltage ceramic capacitors according to claim 2, characterized in that, The molar ratio of titanium dioxide powder to bismuth oxide powder is 2:(1-1.15).

4. The lead-free, high-dielectric-constant, ultra-low-loss dielectric material for high-voltage ceramic capacitors according to claim 2, characterized in that, The titanium dioxide powder has a particle size of 800-1200 mesh.

5. The lead-free, high-dielectric-constant, ultra-low-loss dielectric material for high-voltage ceramic capacitors according to claim 2, characterized in that, The bismuth oxide powder has a particle size of 700-1000 mesh.

6. The lead-free, high-dielectric-constant, ultra-low-loss dielectric material for high-voltage ceramic capacitors according to claim 2, characterized in that, The drying process involves drying at 95-105℃ for 10-15 hours.

7. The lead-free, high-dielectric-constant, ultra-low-loss dielectric material for high-voltage ceramic capacitors according to claim 1, characterized in that, The specified temperature is 815-825℃; the specified time is 95-105min.

8. A method for preparing a lead-free, high-dielectric-constant, ultra-low-loss dielectric material for high-voltage ceramic capacitors according to any one of claims 1-7, characterized in that, Includes the following steps: Step S1: After mixing BaTiO3 and SrTiO3 evenly by molar amount, Bi2Ti2O7, Nb2O5, Cr2O3, Fe2O3 and Dy2O3 are added in sequence. Deionized water is added and the mixture is ball-milled for 5-7 hours. After drying, it is pressed and sintered in sequence. Step S2: Print silver electrodes on the end face and keep warm at 795-805℃ for 13-18 minutes to complete the preparation.

9. The method for preparing lead-free, high-dielectric-constant, ultra-low-loss dielectric material for high-voltage ceramic capacitors according to claim 8, characterized in that, The pressure for compression molding is 295-305 MPa.

10. The method for preparing lead-free, high-dielectric-constant, ultra-low-loss dielectric material for high-voltage ceramic capacitors according to claim 8, characterized in that, The sintering temperature is 1200-1280℃; the sintering holding time is 2-4h.

Images