Dielectric ceramic, method for preparing the same and use thereof

Abstract

The application discloses a kind of dielectric ceramic and its preparation method and application.The dielectric ceramic of the application includes the following mass percentage of components: Bi2O3: 8.3%~17.4%;CaO: 5.5%~14.9%;SrO: 20.6%~34.6%;ZrO2: 24.6%~32.8%;TiO2: 17.9%~25.6%.The preparation method of the dielectric ceramic of the application includes the following steps: 1) preparation intermediate powder;2) intermediate powder is mixed according to stoichiometric ratio, ball milling, drying, then adding binder to granulation, then performing die forming and sintering.The dielectric ceramic of the application has the advantages of large dielectric constant, small dielectric loss, small dielectric constant temperature coefficient, etc., and its preparation process is simple, raw material is low in price, environment-friendly, can be applied in pulse circuit, power conversion, wireless charging and other fields, and has broad application prospect.

Description

Technical Field

[0001] This invention relates to the field of capacitor technology, specifically to a dielectric ceramic, its preparation method, and its application. Background Technology

[0002] With the booming development of the new energy electric vehicle industry, related power electronic components urgently need optimization and upgrading. Capacitors, with their functions of storing charge and DC-AC conversion (blocking DC and passing AC), are key components in the power management and DC-AC conversion systems of new energy electric vehicles. Multilayer ceramic capacitors (MLCCs) have advantages such as small size, wide operating frequency range, and high operating temperature, making them an ideal choice for power electronics applications.

[0003] Traditional high-capacitance MLCCs often use modified ferroelectric ceramic materials (e.g., Type II dielectric ceramics X7R, Z5U, etc.). Their capacitance drops significantly under DC bias, while the equivalent series resistance (ESR) increases substantially, causing severe heat generation and limiting their application in power electronic components. Type I dielectrics, using paraelectric materials, have a dielectric constant that hardly changes with the operating voltage. The most commonly used Type I dielectric is C0G, but its dielectric constant is only 20–40, which is insufficient for high capacitance requirements. Commercial U2J capacitors use calcium zirconate titanate, but its dielectric constant is only 80, still failing to meet the growing demands of practical applications. Traditional calcium titanate and strontium titanate materials have high dielectric constants, 180 and 300 respectively, but their dielectric constant temperature coefficients are relatively large, -1800ppm / ℃ and -3000ppm / ℃ respectively. Moreover, when titanate ceramics are sintered in a reducing atmosphere, titanium ions are easily reduced, which increases dielectric loss. In addition, they cannot meet the requirements of co-firing with base metal electrodes.

[0004] Therefore, developing a dielectric ceramic with a large dielectric constant, low dielectric loss, and small temperature coefficient of dielectric constant is of great significance. Summary of the Invention

[0005] The purpose of this invention is to provide a dielectric ceramic, its preparation method, and its application.

[0006] The technical solution adopted in this invention is:

[0007] A dielectric ceramic comprising the following components by mass percentage:

[0008] Bi2O3: 8.3%–17.4%;

[0009] CaO: 5.5%–14.9%;

[0010] SrO: 20.6%–34.6%;

[0011] ZrO2: 24.6%–32.8%;

[0012] TiO2: 17.9%–25.6%.

[0013] A method for preparing a dielectric ceramic as described above includes the following steps:

[0014] 1) According to the chemical composition formula Bi 2 / 3 The stoichiometric ratios of TiO3, SrTiO3, CaZrO3, and SrZrO3 were determined by weighing Bi2O3, CaCO3, SrCO3, ZrO2, and TiO2, mixing, ball milling, drying, and pre-calcining to obtain Bi2O3, SrTiO3, CaZrO3, and SrZrO3. 2 / 3 TiO3 intermediate powder, SrTiO3 intermediate powder, CaZrO3 intermediate powder and SrZrO3 intermediate powder;

[0015] 2) Change Bi 2 / 3 TiO3 intermediate powder, SrTiO3 intermediate powder, CaZrO3 intermediate powder and SrZrO3 intermediate powder are mixed in stoichiometric ratio, ball-milled, dried, then granulated with a binder, and then molded and sintered to obtain dielectric ceramic.

[0016] Preferably, the purity of Bi2O3, CaCO3, SrCO3, ZrO2 and TiO2 in step 1) is all above 99%.

[0017] Preferably, the ball milling method in step 1) is wet ball milling, and the ball milling time is 30 min to 120 min.

[0018] Preferably, the ball milling device used in step 1) is a planetary ball mill.

[0019] Preferably, the pre-firing in step 1) is carried out in an oxygen-containing atmosphere at a temperature of 1100℃~1200℃ for a time of 1h~6h.

[0020] Preferably, the oxygen-containing atmosphere is an air atmosphere.

[0021] Preferably, the ball milling method in step 2) is wet ball milling, and the ball milling time is 30 min to 120 min.

[0022] Preferably, the ball milling device used in step 2) is a planetary ball mill.

[0023] Preferably, the amount of binder used in step 2) is 0.25% to 1% of the total mass of the ceramic powder.

[0024] Preferably, the adhesive in step 2) is at least one of polyvinyl alcohol and polyvinyl butyral.

[0025] More preferably, the adhesive in step 2) is polyvinyl alcohol.

[0026] Preferably, the sintering in step 2) is carried out in an oxygen-containing atmosphere at a temperature of 1200℃~1350℃ for a time of 1h~6h.

[0027] Preferably, the oxygen-containing atmosphere is an air atmosphere.

[0028] A capacitor comprising the aforementioned dielectric ceramic.

[0029] A new energy electric vehicle includes the aforementioned capacitor.

[0030] The beneficial effects of this invention are: the dielectric ceramic of this invention has the advantages of large dielectric constant, low dielectric loss, and small dielectric constant temperature coefficient, and its preparation process is simple, the raw materials are inexpensive, and it is environmentally friendly. It can be applied in pulse circuits, power conversion, wireless charging and other fields, and has broad application prospects.

[0031] Specifically:

[0032] 1) The dielectric ceramic of the present invention has a large dielectric constant (117.8~206.2), a small dielectric loss (<0.001), a small dielectric constant temperature coefficient (-1026ppm / ℃~-656ppm / ℃), and the dielectric constant temperature coefficient is adjustable;

[0033] 2) The dielectric ceramic of the present invention does not change with the working voltage within the working temperature range of -55℃ to 155℃. The dielectric constant changes almost linearly with temperature, and it can be applied in wireless charging, power conversion, resonant converter and other fields.

[0034] 3) The dielectric ceramic of the present invention can be sintered at 1200℃~1350℃, which has a low sintering temperature and low energy consumption;

[0035] 4) The dielectric ceramic of the present invention uses common elements that are clean and pollution-free, does not contain expensive rare earth elements, and the raw materials are inexpensive and environmentally friendly. Attached Figure Description

[0036] Figure 1 The image shows the XRD pattern of the dielectric ceramic of Example 6.

[0037] Figure 2 The graph shows the rate of change of capacitance temperature of the dielectric ceramic in Example 6 as a function of temperature. Detailed Implementation

[0038] The present invention will be further explained and described below with reference to specific embodiments.

[0039] Examples 1-15 and Comparative Examples 1-2:

[0040] The raw material ratios (by mass percentage) and dielectric property test results of the dielectric ceramics in Examples 1-15 and Comparative Examples 1-2 are shown in the table below:

[0041] Table 1. Raw material ratio and dielectric property test results of dielectric ceramics.

[0042]

[0043]

[0044] Note:

[0045] ε r (Dielectric constant): Tested using an E4294A impedance analyzer at a frequency of 100kHz.

[0046] τ ε (Temperature coefficient of dielectric constant): Tested using an E4294A impedance analyzer at a frequency of 100kHz.

[0047] The dielectric ceramics of Examples 1-15 and Comparative Example 2 all have a dielectric loss of less than 0.001 at room temperature, while the dielectric ceramic of Comparative Example 1 has a dielectric loss of greater than 0.001 at room temperature.

[0048] The preparation method of the above-mentioned dielectric ceramic is as follows:

[0049] 1) According to the chemical composition formula Bi 2 / 3 The stoichiometric ratio of Bi₂O₃, CaCO₃, SrCO₃, ZrO₂, and TiO₂ was determined by weighing out Bi₂O₃, CaCO₃, SrCO₃, ZrO₂, and TiO₂, all with a purity of over 99%. The mixture was then placed in a planetary ball mill and milled for 30-120 minutes at a speed of 300 r / min. The milling jar was made of polytetrafluoroethylene (PTFE), the milling media were 1 mm diameter zirconium dioxide balls, and the solvent was alcohol. The mass ratio of milling media, raw material powder, and alcohol was 1:1:1. After drying, the mixture was pre-calcined in air at 1100℃-1200℃ for 1-6 hours to obtain Bi₂O₃. 2 / 3TiO3 intermediate powder, SrTiO3 intermediate powder, CaZrO3 intermediate powder and SrZrO3 intermediate powder;

[0050] 2) Change Bi 2 / 3TiO3 intermediate powder, SrTiO3 intermediate powder, CaZrO3 intermediate powder, and SrZrO3 intermediate powder are mixed according to stoichiometric ratio and placed in a planetary ball mill for 30 min to 120 min. The planetary ball mill rotates at 300 r / min. The ball mill jar is made of polytetrafluoroethylene, the ball milling media is 1 mm diameter zirconia balls, and the solvent is alcohol. The mass ratio of ball milling media, raw material powder, and alcohol is 1:1:1. After drying, a 5% to 10% polyvinyl alcohol solution is added for granulation. The amount of polyvinyl alcohol solution is 5% to 10% of the total mass of ceramic powder. Then, it is uniaxially pressurized to form a circular green body with a diameter of 13 mm and a thickness of 1 mm. Finally, it is sintered in air at a temperature of 1200℃ to 1350℃ for 1 h to 6 h to obtain dielectric ceramic.

[0051] As shown in Table 1:

[0052] a) The dielectric ceramics of Examples 1 to 15 have dielectric constants of 117.8 to 206.2, dielectric loss of <0.001 at room temperature, and dielectric constant temperature coefficients of -1026ppm / ℃ to -656ppm / ℃. This indicates that the dielectric ceramics of the present invention have large dielectric constants, low dielectric loss, and small dielectric constant temperature coefficients, and the dielectric constant temperature coefficients are adjustable.

[0053] b) The dielectric ceramic of Comparative Example 1 has too low a ZrO2 content and too high a TiO2 content, and its dielectric constant temperature coefficient is significantly higher than that of the dielectric ceramics of Examples 1 to 15.

[0054] c) The dielectric ceramic of Comparative Example 2 does not contain Bi2O3, and its dielectric constant temperature coefficient is significantly higher than that of the dielectric ceramics of Examples 1 to 15, while its dielectric constant is significantly lower than that of the dielectric ceramics of Examples 1 to 15.

[0055] The X-ray diffraction (XRD) pattern of the dielectric ceramic in Example 6 is shown below. Figure 1 As shown in the figure, the rate of change of capacitive temperature (TCC) varies with temperature. Figure 2 As shown.

[0056] Depend on Figure 1 It can be seen that the main crystalline phase of the dielectric ceramic in Example 6 is the perovskite phase.

[0057] Depend on Figure 2 It can be seen that the capacitance-temperature change rate of the dielectric ceramic in Example 6 changes almost linearly with temperature.

[0058] In summary, the dielectric ceramic of this invention has a high dielectric constant, low dielectric loss, and a small temperature coefficient of dielectric constant. Furthermore, the temperature coefficient of dielectric constant is adjustable. Within the operating temperature range of -55℃ to 155℃, the dielectric constant does not change with the operating voltage, and the dielectric constant changes almost linearly with temperature. Moreover, the dielectric ceramic of this invention can be sintered at 1200℃ to 1350℃, which is a relatively low sintering temperature and consumes less energy. It uses clean and pollution-free common elements, does not contain expensive rare earth elements, and the raw materials are inexpensive and environmentally friendly. It can be applied in wireless charging, power conversion, resonant converters, and other fields, and has a very broad application prospect.

[0059] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A dielectric ceramic, characterized in that, Includes the following components by mass percentage: Bi2O3: 8.3%~17.4%; CaO: 5.5%~14.9%; SrO: 20.6%~34.6%; ZrO2: 24.6%~32.8%; TiO2: 17.9%~25.6%; The dielectric ceramic is prepared by a method comprising the following steps: 1) According to the chemical composition formula Bi 2 / 3 The stoichiometric ratios of TiO3, SrTiO3, CaZrO3, and SrZrO3 were determined by weighing Bi2O3, CaCO3, SrCO3, ZrO2, and TiO2, mixing, ball milling, drying, and pre-calcining to obtain Bi2O3, SrTiO3, CaZrO3, and SrZrO3. 2 / 3 TiO3 intermediate powder, SrTiO3 intermediate powder, CaZrO3 intermediate powder and SrZrO3 intermediate powder; 2) Change Bi 2 / 3 TiO3 intermediate powder, SrTiO3 intermediate powder, CaZrO3 intermediate powder and SrZrO3 intermediate powder are mixed in stoichiometric ratio, ball-milled, dried, then granulated with a binder, and then molded and sintered to obtain dielectric ceramic.

2. The dielectric ceramic according to claim 1, characterized in that: In step 1), the purity of Bi2O3, CaCO3, SrCO3, ZrO2 and TiO2 is all above 99%.

3. The dielectric ceramic according to claim 1 or 2, characterized in that: Step 1) The ball milling method is wet ball milling, and the ball milling time is 30 min to 120 min.

4. The dielectric ceramic according to claim 1 or 2, characterized in that: Step 1) The pre-firing is carried out in an oxygen-containing atmosphere at a temperature of 1100℃~1200℃ for 1h~6h.

5. The dielectric ceramic according to claim 1, characterized in that: Step 2) The ball milling method is wet ball milling, and the ball milling time is 30 min to 120 min.

6. The dielectric ceramic according to claim 1 or 5, characterized in that: Step 2) The amount of binder used is 0.25% to 1% of the total mass of ceramic powder; Step 2) The binder is at least one of polyvinyl alcohol and polyvinyl butyral.

7. The dielectric ceramic according to claim 1 or 5, characterized in that: Step 2) The sintering is carried out in an oxygen-containing atmosphere at a temperature of 1200℃~1350℃ for 1h~6h.

8. A capacitor, characterized in that, It includes the dielectric ceramic according to any one of claims 1 to 7.

9. A new energy electric vehicle, characterized in that, It includes the capacitor as described in claim 8.

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