Paraelectric dielectric ceramic as well as preparation method and application thereof

Abstract

The invention discloses paraelectric dielectric ceramic as well as a preparation method and application thereof. The paraelectric dielectric ceramic provided by the invention comprises the following components in percentage by mass: 23.7-38.6% of SrO; 8.9% to 20.6% of Bi2O3 (bismuth oxide); 0% to 12.5% of CaO; tiO2: 30.4% to 35.6%; and 12.1% to 20.1% of ZrO2. The paraelectric dielectric ceramic has the advantages of large dielectric constant, low dielectric loss, small dielectric constant temperature coefficient, suitability for co-firing with a copper electrode and the like, can be used in the fields of oscillators, resonant circuits, power conversion and the like, and is simple in preparation method, low in sintering temperature, low in raw material price, environment-friendly, pollution-free and suitable for industrial production. The method is suitable for large-scale industrial production and application.

Description

Technical Field

[0001] The present invention relates to the technical field of dielectric ceramics, and particularly relates to a paraelectric dielectric ceramic, a preparation method thereof, and an application thereof. Background Art

[0002] The basic function of a capacitor is to store charge and block direct current, and its functions in a circuit include decoupling, bypassing, filtering, tuning, oscillation, and voltage division, etc. With the rapid rise of artificial intelligence (AI) technology, the demand for high-computing-power GPUs and CPUs is becoming more and more urgent. However, as the computing power of GPUs and CPUs increases, their power consumption will also increase rapidly. In order to ensure the stable operation of servers, higher performance requirements (such as high capacitance and low loss, etc.) are put forward for the basic component, the multi-layer ceramic capacitor (MLCC).

[0003] Traditional high-capacitance Class II MLCCs use ferroelectric ceramic materials. Ferroelectric materials have relatively high dielectric losses, and the capacitance value will drop significantly under a DC bias voltage, resulting in a significant increase in the equivalent series resistance (ESR), and ultimately causing serious problems such as overheating of the components. Therefore, the performance instability of ferroelectric phase materials determines that they cannot be used in high-power electronic components. Class I dielectrics using paraelectric materials have low dielectric losses, and the dielectric constant hardly changes with the operating voltage, and they are more suitable for high-power-consuming electronic components. However, the dielectric constant of commercially available C0G capacitor materials in Class I dielectrics is only 20 - 40, and the dielectric constant of commercially available U2J capacitor materials is also only 80, which simply cannot meet the growing demand for high dielectric constants. In addition, using copper electrodes to replace silver electrodes and silver-palladium electrodes is the main development trend of MLCC co-firing, but existing dielectric ceramics are not suitable for co-firing with copper electrodes.

[0004] Therefore, it is of great significance to develop a paraelectric dielectric ceramic with a large dielectric constant, low dielectric loss, a small temperature coefficient of dielectric constant, and suitable for co-firing with copper electrodes. Summary of the Invention

[0005] The purpose of the present invention is to provide a paraelectric dielectric ceramic, a preparation method thereof, and an application thereof.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A paraelectric dielectric ceramic, which comprises the following components in mass percentage:

[0008] SrO: 23.7% - 38.6%;

[0009] Bi2O3: 8.9% - 20.6%;

[0010] CaO: 0% to 12.5%;

[0011] TiO2: 30.4% to 35.6%;

[0012] ZrO2: 12.1% to 20.1%.

[0013] Preferably, the dielectric constant of the paraelectric dielectric ceramic is 199.8 to 410.0, the dielectric loss is <0.003, and the temperature coefficient of dielectric constant is -1947 ppm / °C to -1238 ppm / °C.

[0014] A method for preparing a paraelectric dielectric ceramic as described above includes the following steps:

[0015] 1) Weigh SrCO3 powder, Bi2O3 powder, CaCO3 powder, TiO2 powder and ZrO2 powder according to the stoichiometric ratio, mix, ball mill, dry, pre-sinter to obtain ceramic precursor powder;

[0016] 2) Mix the ceramic precursor powder and sintering aid, ball mill, dry, then add a binder for granulation, press molding, sinter to obtain the paraelectric dielectric ceramic.

[0017] Preferably, the purity of the SrCO3 powder, Bi2O3 powder, CaCO3 powder, TiO2 powder and ZrO2 powder in step 1) is above 99.5%.

[0018] Preferably, the ball milling method in step 1) is wet ball milling, and the ball milling time is 30 min to 120 min.

[0019] Preferably, the ball milling equipment used in step 1) is a planetary ball mill.

[0020] Preferably, the pre-sintering in step 1) is carried out in an oxygen-containing atmosphere at a temperature of 1100°C to 1200°C, and the pre-sintering time is 1 h to 6 h.

[0021] Preferably, the oxygen-containing atmosphere is an air atmosphere.

[0022] Preferably, the dosage of the sintering aid in step 2) is 1.5% to 3.0% of the weight of the ceramic precursor powder.

[0023] Preferably, the sintering aid in step 2) includes MnCO3, Li2CO3 and glass powder.

[0024] Preferably, the mass ratio of MnCO3, Li2CO3, glass powder is 1:0.8 to 1.2:1 to 4.

[0025] Preferably, the glass powder comprises the following components in mass percentage: SiO2: 60%; Al2O3: 10%; CaO: 10%; K2O: 2%; Na2O: 1%; B2O3: 3%; ZnO: 5.3%; BaO: 8.7%.

[0026] Preferably, the ball milling method in step 2) is wet ball milling, and the ball milling time is 30 min to 120 min.

[0027] Preferably, the ball milling equipment used in step 2) is a planetary ball mill.

[0028] Preferably, the dosage of the binder in step 2) is 5% to 10% of the weight of the ceramic precursor powder.

[0029] Preferably, the binder in step 2) is a polyvinyl alcohol solution with a mass fraction of 5% to 10%.

[0030] Preferably, the sintering in step 2) is carried out under the conditions of a nitrogen atmosphere and a temperature of 1000°C to 1100°C, and the sintering time is 1 h to 6 h.

[0031] A multilayer ceramic capacitor, which comprises the above-mentioned paraelectric dielectric ceramic.

[0032] The beneficial effects of the present invention are as follows: The paraelectric dielectric ceramic of the present invention has the advantages of large dielectric constant, low dielectric loss, small temperature coefficient of dielectric constant, and being suitable for co-firing with copper electrodes. It can be used in fields such as oscillators, resonant circuits, and power conversion. Moreover, its preparation method is simple, the sintering temperature is low, the raw material price is low, and it is environmentally friendly and pollution-free, making it suitable for large-scale industrial production and application.

[0033] Specifically:

[0034] 1) The paraelectric dielectric ceramic of the present invention has a large dielectric constant (199.8 to 410.0), low dielectric loss (<0.003), a small temperature coefficient of dielectric constant (-1947 ppm / °C to -1238 ppm / °C), and is suitable for co-firing with copper electrodes, and can be used in fields such as oscillators, resonant circuits, and power conversion;

[0035] 2) The paraelectric dielectric ceramic of the present invention does not change with the working voltage within the working temperature range of -55°C to 125°C, and the dielectric constant changes almost linearly with temperature;

[0036] 3) The sintering temperature of the paraelectric dielectric ceramic of the present invention does not exceed 1100°C, the sintering temperature is low, and the energy consumption in the preparation process is low;

[0037] 4) The preparation method of the paraelectric dielectric ceramic of the present invention is simple, and the raw materials are inexpensive (without expensive rare earth elements), safe and environmentally friendly (all are common elements that are clean and pollution-free), and are suitable for large-scale industrial production and application. Description of the Drawings

[0038] Figure 1 XRD pattern of the paraelectric dielectric ceramic of Example 2.

[0039] Figure 2 Dielectric constant-temperature relationship curve of the paraelectric dielectric ceramic of Example 2. Detailed Description of the Invention

[0040] The present invention will be further explained and described below in conjunction with specific embodiments.

[0041] Examples 1-8 and Comparative Examples 1-2:

[0042] The compositions (by mass percentage) and dielectric property test results of the paraelectric dielectric ceramics of Examples 1-8 and Comparative Examples 1-2 are shown in the following table:

[0043] Table 1 Compositions and Dielectric Property Test Results of Paraelectric Dielectric Ceramics

[0044]

[0045]

[0046] Note:

[0047] The sintering aid consists of MnCO3, Li2CO3 and glass powder. The dosages of MnCO3 and Li2CO3 are both 0.5% of the weight of the ceramic precursor powder, and the dosage of the glass powder is 0% - 2.0% of the weight of the ceramic precursor powder.

[0048] The glass powder consists of the following components by mass percentage: SiO2: 60%; Al2O3: 10%; CaO: 10%; K2O: 2%; Na2O: 1%; B2O3: 3%; ZnO: 5.3%; BaO: 8.7%.

[0049] ε r (Dielectric constant): Tested using an impedance analyzer E4981A, and the test frequency is 1 MHz.

[0050] τ ε (Temperature coefficient of dielectric constant): Tested using an impedance analyzer E4981A, and the test frequency is 1 MHz.

[0051] The dielectric losses of the paraelectric dielectric ceramics of Examples 1-8 and Comparative Examples 1-2 at room temperature are all less than 0.003.

[0052] The preparation method of the above-mentioned paraelectric dielectric ceramic is as follows:

[0053] 1) Weigh SrCO3 powder, Bi2O3 powder, CaCO3 powder, TiO2 powder and ZrO2 powder according to the stoichiometric ratio. The purities of SrCO3 powder, Bi2O3 powder, CaCO3 powder, TiO2 powder and ZrO2 powder are all above 99.5%. Mix them and place them in a planetary ball mill for ball milling for 30 min to 120 min. The rotation speed of the planetary ball mill is 300 r / min. The material of the ball mill tank is nylon. The ball milling medium is zirconia balls with a diameter of 1 mm. The solvent is alcohol. The mass ratio of the ball milling medium, raw material powder and alcohol is 1:1:1. Dry them, and then pre-burn them for 1 h to 6 h under the conditions of an air atmosphere and a temperature of 1100 °C to 1200 °C to obtain ceramic precursor powder;

[0054] 2) Mix the ceramic precursor powder and the sintering aid, place them in a planetary ball mill for ball milling for 30 min to 120 min. The rotation speed of the planetary ball mill is 300 r / min. The material of the ball mill tank is nylon. The ball milling medium is zirconia balls with a diameter of 1 mm. The solvent is alcohol. The mass ratio of the ball milling medium, raw material powder and alcohol is 1:1:1. Dry them, and then add a polyvinyl alcohol solution with a mass fraction of 5% to 10% for granulation. The dosage of the polyvinyl alcohol solution is 5% to 10% of the weight of the ceramic precursor powder. Then, make a disc-shaped green body with a diameter of 13 mm and a thickness of 1 mm by uniaxial pressing. Then, sinter it for 1 h to 6 h under the conditions of a nitrogen atmosphere and a temperature of 1000 °C to 1100 °C, and the heating rate is 2 °C / min to 5 °C / min, thus obtaining the paraelectric dielectric ceramic.

[0055] As can be seen from Table 1:

[0056] a) The dielectric constants of the paraelectric dielectric ceramics in Examples 1 to 8 are 199.8 to 410.0, the dielectric loss at room temperature is <0.003, and the temperature coefficient of dielectric constant is -1947 ppm / °C to -1238 ppm / °C, indicating that the paraelectric dielectric ceramic of the present invention has a large dielectric constant, a small dielectric loss, a low and adjustable temperature coefficient of dielectric constant;

[0057] b) As the dosage of the glass powder in Examples 6 to 8 increases, the sintering temperature will decrease accordingly, indicating that using the glass powder as a sintering aid can effectively reduce the sintering temperature;

[0058] c) In the paraelectric dielectric ceramic of Comparative Example 1, the calcium content is too high, the titanium content is too low, and the zirconium content is too high. Its dielectric constant is significantly lower than that of the paraelectric dielectric ceramics in Examples 1 to 8, and the paraelectric dielectric ceramic of Comparative Example 1 does not use glass powder during preparation, and the sintering temperature is relatively high;

[0059] d) The content of titanium in the paraelectric dielectric ceramic of Comparative Example 2 is too low and the content of zirconium is too high, and its dielectric constant is significantly lower than that of the paraelectric dielectric ceramics of Examples 1 to 8.

[0060] The X-ray diffraction (XRD) pattern of the paraelectric dielectric ceramic of Example 2 is as Figure 1 shown, and the dielectric constant-temperature relationship curve is as Figure 2 shown.

[0061] It can be seen from Figure 1 that the main crystal phase of the paraelectric dielectric ceramic of Example 2 is a cubic perovskite phase.

[0062] It can be seen from Figure 2 that the dielectric constant of the paraelectric dielectric ceramic of Example 2 changes almost linearly with temperature.

[0063] In summary, it can be known that the paraelectric dielectric ceramic of the present invention has a large dielectric constant and can be serialized, low dielectric loss, low and adjustable temperature coefficient of dielectric constant. Moreover, the raw materials used in the paraelectric dielectric ceramic of the present invention do not contain rare earth elements and are inexpensive. In addition, the paraelectric dielectric ceramic of the present invention has low high-frequency loss and the dielectric constant does not change with the working voltage within the working temperature range of -55°C to 125°C, and the dielectric constant changes almost linearly with temperature, and can be used in fields such as oscillators, resonant circuits, and power conversion.

[0064] 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 other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and shall be included in the protection scope of the present invention.

Claims

1. A paraelectric dielectric ceramic, characterized in that, Comprising components with the following mass percentages: SrO: 23.7% to 38.6%; Bi2O3: 8.9% to 20.6%; CaO: 0% to 12.5%; TiO2: 30.4% to 35.6%; ZrO2: 12.1% to 20.1%.

2. The paraelectric dielectric ceramic according to claim 1, wherein: The dielectric constant of the paraelectric dielectric ceramic is 199.8 to 410.0, the dielectric loss is <0.003, and the temperature coefficient of dielectric constant is -1947 ppm / °C to -1238 ppm / °C.

3. A method for preparing a paraelectric dielectric ceramic as described in claim 1 or 2, characterized in that, Including the following steps: 1) Weigh SrCO3 powder, Bi2O3 powder, CaCO3 powder, TiO2 powder and ZrO2 powder according to the stoichiometric ratio, mix, ball mill, dry, pre-sinter to obtain ceramic precursor powder; 2) Mix the ceramic precursor powder and sintering aid, ball mill, dry, then add a binder for granulation, press molding, sinter to obtain the paraelectric dielectric ceramic.

4. The preparation method according to claim 3, characterized in that: The purities of the SrCO3 powder, Bi2O3 powder, CaCO3 powder, TiO2 powder and ZrO2 powder in step 1) are all above 99.5%.

5. The preparation method according to claim 3 or 4, characterized in that: The pre-sintering in step 1) is carried out in an oxygen-containing atmosphere at a temperature of 1100°C to 1200°C, and the pre-sintering time is 1 h to 6 h.

6. The preparation method according to claim 3, characterized in that: The dosage of the sintering aid in step 2) is 1.5% to 3.0% of the weight of the ceramic precursor powder; the sintering aid in step 2) includes MnCO3, Li2CO3 and glass powder; the mass ratio of MnCO3, Li2CO3, and glass powder is 1:0.8 to 1.2:1 to 4.

7. The preparation method according to claim 3 or 6, characterized in that: The dosage of the binder in step 2) is 5% to 10% of the weight of the ceramic precursor powder; the binder in step 2) is a polyvinyl alcohol solution with a mass fraction of 5% to 10%.

8. The preparation method according to claim 3 or 6, characterized in that: The sintering in step 2) is carried out in a nitrogen atmosphere at a temperature of 1000°C to 1100°C, and the sintering time is 1 h to 6 h.

9. The preparation method according to any one of claims 3, 4 and 6, characterized in that: The ball milling method in step 1) is wet ball milling, and the ball milling time is 30 min to 120 min; the ball milling method in step 2) is wet ball milling, and the ball milling time is 30 min to 120 min.

10. A multilayer ceramic capacitor, characterized in that, Comprising the paraelectric dielectric ceramic described in claim 1 or 2.

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