An X9R type MLCC ceramic material and its preparation method

Abstract

The present invention discloses an X9R type MLCC ceramic material and a preparation method thereof. The invention provides an X9R type MLCC ceramic material with a chemical general formula of: (1-x)(K 0.85 Na 0.15 )NbO3-xBaTi 0.8 Dy 0.2 O3, where 0.1 ≤ x ≤ 0.2. This material has a relatively high dielectric constant and a relatively low dielectric loss, and maintains good temperature stability within a wide temperature range, capable of meeting the requirements of X9R type MLCC applications.

Description

Technical Field

[0001] The present invention relates to the field of dielectric ceramic materials of ceramic capacitors, and in particular to an X9R type MLCC ceramic material and a preparation method thereof. Background Art

[0002] With the rapid development of electronic technology, ceramic capacitors, as an important passive component, are widely used in electronic equipment, especially in high-demand fields such as communications, automotive electronics, and industrial control. Multilayer ceramic capacitors (MLCCs) have become mainstream products on the market due to their miniaturization, high capacity, and low loss.

[0003] The X9R standard stipulates that the operating temperature range of the capacitor is -55℃ to 200℃, and the capacitance change rate must be less than ±15% within this temperature range. In order to meet the application requirements of X9R MLCC, the dielectric constant of the ceramic dielectric material must be high and be able to maintain stable dielectric properties over a wide temperature range, especially the dielectric loss in the low temperature area needs to be as low as possible. However, the ceramic materials used in most commercial MLCCs on the market still have certain limitations.

[0004] Traditional BaTiO-based 3 Ceramic materials of the system are widely used in MLCC. Although such materials can meet the X9R standard to a certain extent, they have problems such as low dielectric constant and high dielectric loss in low temperature zone. For example, the domestic invention patent CN112110723A discloses a La 2 O 3 and Bi(Mg 0.5 Ti 0.5 ) 3 Co-doped BaTiO 3 Although ceramics can meet the application requirements of X9R MLCC, the dielectric constant of this material is low in the low temperature region, and its dielectric loss data is not disclosed. In addition, although the potassium sodium niobate-based dielectric ceramic material disclosed in patent CN115784741A has a high dielectric constant, its dielectric loss in the low temperature region is unknown, and the problem of performance degradation at low temperatures has not been completely solved.

[0005] At present, there is still a lack of a ceramic material with high dielectric constant and low dielectric loss in a wide temperature range on the market. Therefore, there is an urgent need to develop a new dielectric ceramic material suitable for X9R type MLCC, which has wide temperature stability, high dielectric constant and low dielectric loss to meet higher performance requirements. Summary of the invention

[0006] The present invention aims to solve the problems of low dielectric constant and high dielectric loss in low temperature region in existing X9R type MLCC ceramic materials. The present invention provides an X9R type MLCC ceramic material and a preparation method thereof. The ceramic material provided by the present invention has a high dielectric constant, low dielectric loss, and maintains good temperature stability in a wide temperature range, which can meet the application requirements of X9R type MLCC.

[0007] The present invention provides an X9R type MLCC ceramic material, the general chemical formula of which is: (1-x)(K 0.85 Na 0.15 )NbO 3 -xBaTi 0.8 Dy 0.2 O 3 , where the value of x is 0.1≤x≤0.2.

[0008] In the present invention, the chemical formula of the X9R type MLCC ceramic material is: 0.9(K 0.85 Na 0.15 )NbO 3 -0.1BaTi 0.8 Dy 0.2 O 3 , or 0.8(K 0.85 Na 0.15 )NbO 3 -0.2BaTi 0.8 Dy 0.2 O 3 .

[0009] The present invention also provides a method for preparing an X9R type MLCC ceramic material, which comprises the following steps: (1) preparing a X9R type MLCC ceramic material according to the general chemical formula (1-x)(K 0.85 Na 0.15 )NbO 3 -xBaTi 0.8 Dy 0.2 O 3 Weigh K in the stoichiometric ratio 2 CO 3 、Na 2 CO 3 , Nb 2 O 5 、BaCO 3 、TiO 2 and Dy 2 O 3 The raw material, wherein the value of x is 0.1≤x≤0.2, is pre-dried to obtain a pre-dried raw material.

[0010] (2) Mix the pre-dried raw materials, zirconia balls and absolute ethanol, place them in a nylon jar, and use a planetary ball mill to perform ball milling to obtain the first slurry.

[0011] (3) Dry the first slurry to obtain a mixed powder; then perform high-temperature calcination, and cool to room temperature after calcination to obtain the first calcined powder.

[0012] (4) Mix the first calcined powder, zirconia balls and absolute ethanol, place them in a nylon jar, and use a planetary ball mill to perform secondary ball milling to obtain the second slurry.

[0013] (5) Dry the second slurry, and sieve it through a sieve to obtain the second calcined powder.

[0014] (6) Add polyvinyl alcohol to the second calcined powder for granulation, and finally press the granulated powder into a ceramic wafer under a pressure of 100 - 200 MPa.

[0015] (7) Heat the ceramic wafer to 600 °C in an air atmosphere and keep it warm for 4 hours for debinding treatment to obtain a green ceramic wafer.

[0016] (8) Sinter the green ceramic wafer at high temperature, and cool to room temperature after sintering to obtain a sintered ceramic wafer.

[0017] (9) At room temperature, apply silver paste on the surface of the sintered ceramic wafer, heat it to 600 °C, keep it warm for 1 hour, and then cool to room temperature to obtain the X9R type MLCC ceramic material.

[0018] In the present invention, in step (1), the temperature of the pre-drying is 70 - 90 °C, and the time of the pre-drying is 0.5 - 16 hours.

[0019] In the present invention, in step (2), the weight ratio of the pre-dried raw materials, zirconia balls and absolute ethanol is 1:(8 - 12):(4 - 6), preferably 1:10:5.

[0020] In the present invention, in steps (2) and (4), the time of the ball milling is 16 - 32 hours, and the rotation speed of the ball milling is 100 - 300 r / min.

[0021] In the present invention, in step (3), the temperature of the drying is 80 - 120 °C, the time of the drying is 8 - 16 hours, the temperature of the calcination is 800 - 1000 °C, and the time of the calcination is 3 - 7 hours.

[0022] In the present invention, in step (4), the weight ratio of the first calcined powder, zirconia balls and absolute ethanol is 1:(8 - 12):(4 - 6), preferably 1:10:5.

[0023] In the present invention, in step (4), the ball milling time is 16 - 32 hours, and the rotation speed of the ball milling is 300 - 500 r / min.

[0024] In the present invention, in step (5), the drying temperature is 80 - 120 °C, and the drying time is 8 - 16 hours.

[0025] In the present invention, in step (5), the sieve mesh is a 60 - 100 mesh sieve, preferably an 80 - mesh sieve.

[0026] In the present invention, in step (6), the weight ratio of the second calcined powder to the polyvinyl alcohol is 1:(0.02 - 0.1); preferably 1:0.03, 1:0.05 or 1:0.07.

[0027] In the present invention, in step (8), the high - temperature sintering temperature is 1000 - 1300 °C, and the high - temperature sintering time is 3 - 5 hours.

[0028] On the basis of conforming to the common knowledge in the art, the above - mentioned preferred conditions can be combined arbitrarily to obtain various preferred examples of the present invention.

[0029] The reagents and raw materials used in the present invention are all commercially available.

[0030] The positive and progressive effects of the present invention are as follows: an X9R - type MLCC ceramic material with a relatively high dielectric constant, a relatively low dielectric loss, and a wide temperature stability is obtained. This material has good temperature stability in the low - temperature region, can work stably in a wider temperature range, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is the powder X - ray diffraction (PXRD) pattern of the ceramic materials 1 - 5 prepared in Examples 1 - 5.

[0032] Figure 2 It is the dielectric temperature spectrum of the ceramic material 1 prepared in Example 1 tested in the temperature range of - 60 to 300 °C.

[0033] Figure 3 It is the dielectric temperature spectrum of the ceramic material 2 prepared in Example 2 tested in the temperature range of - 60 to 300 °C.

[0034] Figure 4 It is the dielectric temperature spectrum of the ceramic material 3 prepared in Example 3 tested in the temperature range of - 60 to 300 °C.

[0035] Figure 5 It is the dielectric temperature spectrum of the ceramic material 4 prepared in Example 4 tested in the temperature range of - 60 to 300 °C.

[0036] Figure 6 The dielectric temperature spectrum obtained by testing the ceramic material 5 prepared in Example 5 in the temperature range of -60 to 300 °C.

[0037] Figure 7 Scanning electron microscope (SEM) photograph of the ceramic material 1 prepared in Example 1.

[0038] Figure 8 Scanning electron microscope (SEM) photograph of the ceramic material 2 prepared in Example 2. Detailed implementation mode

[0039] The present invention will be further described below by way of examples, but the present invention is not limited to the scope of the described examples. For the experimental methods without specific conditions in the following examples, they are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0040] Example 1: Weigh the raw materials according to the stoichiometric ratio of the chemical general formula 0.9(K 0.85 Na 0.15 )NbO 3 -0.1BaTi 0.8 Dy 0.2 O 3 , namely K 2 CO 3 , Na 2 CO 3 , Nb 2 O 5 , BaCO 3 , TiO 2 and Dy 2 O 3 . Place them in an oven and pre-dry at 75 °C for 12 hours to remove the moisture in the raw materials.

[0041] Mix the pre-dried raw materials, zirconia balls and the ball-milling medium anhydrous ethanol in a weight ratio of 1:10:5, place them in a nylon pot, and carry out ball-milling mixing on a planetary ball mill. The ball-milling time is set to 24 hours and the ball-milling speed is 200 r / min. Through the ball-milling process, the raw materials are fully mixed to form a uniform first slurry.

[0042] The first slurry after ball-milling is dried at 100 °C for 12 hours to obtain a mixed powder. Subsequently, the powder is loaded into a corundum crucible and placed in a muffle furnace, and calcined at 900 °C for 5 hours, with a heating rate of 10 °C / min. After calcination, the calcined product is cooled to room temperature to obtain a first calcined powder.

[0043] The first calcined powder, zirconia balls and anhydrous ethanol as the ball-milling medium are mixed again at a weight ratio of 1:10:5, and secondary ball-milling is carried out. The ball-milling time is 24 hours and the ball-milling speed is 400 r / min. The second slurry obtained after ball-milling is dried again at 100 °C for 12 hours, and then passed through an 80-mesh sieve to obtain the second calcined powder.

[0044] 5% by mass of polyvinyl alcohol is added to the second calcined powder as a binder for granulation. Then, the granulated powder is pressed into a ceramic wafer with a diameter of 12 mm and a thickness of about 1.5 mm under a pressure of 150 MPa.

[0045] The pressed ceramic wafer is loaded into a corundum crucible and placed in a muffle furnace. It is heated to 600 °C at a heating rate of 4 °C / min in an air atmosphere and held for 4 hours for debinding treatment. After the debinding treatment, the green body of the ceramic wafer is sintered at 1150 °C for 4 hours, cooled to room temperature after sintering, and the final ceramic material is obtained.

[0046] At room temperature, a layer of silver paste is evenly coated on the surface of the ceramic wafer, and then the ceramic wafer is heated to 600 °C at a heating rate of 4 °C / min and held for 1 hour. After holding, it is cooled to room temperature again, and finally ceramic material 1 is obtained.

[0047] The obtained ceramic material 1 is subjected to powder X-ray diffraction (PXRD) and dielectric property tests. The dielectric constant and dielectric loss are measured and calculated by an Agilent 4194A impedance analyzer. The specific conditions for the dielectric test are: the test frequency is 1 kHz, and the temperature range for the variable-temperature test is from -60 °C to 300 °C. The calculation formula for the dielectric constant (ε) is ε = 14.4(C×d) / D 2 , where C is the capacitance value of the sample read by the instrument; d is the thickness of the ceramic material in mm; D is the diameter of the ceramic material in mm. The dielectric loss is directly read and recorded by the Agilent 4194A impedance analyzer at a test frequency of 1 kHz. The calculation formula for the dielectric constant change rate is (C t -C 25℃ ) / C 25℃ ×100%, C t is the capacitance value of the ceramic material at temperature t, and C 25℃ is the capacitance value of the ceramic material at 25 °C.

[0048] The PXRD picture of sample 1 is as Figure 1 shown, and the dielectric property test results are as Figure 2 shown.

[0049] Example 2: The preparation method of Example 2 is basically the same as that of Example 1, and the main difference is that according to the chemical general formula 0.8(K 0.85Na 0.15 )NbO 3 -0.2BaTi 0.8 Dy 0.2 O 3 Weigh K according to the stoichiometric ratio of 2 CO 3 , Na 2 CO 3 , Nb 2 O 5 , BaCO 3 , TiO 2 and Dy 2 O 3 raw materials. Finally, ceramic material 2 is obtained for powder X-ray diffraction (PXRD) and dielectric property tests. Using the same analysis method as in Example 1. The PXRD pattern of sample 2 is as shown in Figure 1 , and the dielectric property test results are as shown in Figure 3 .

[0050] Example 3: The preparation method of Example 3 is basically the same as that of Example 1. The main difference is that according to the chemical general formula of 0.95(K 0.85 Na 0.15 )NbO 3 -0.05BaTi 0.8 Dy 0.2 O 3 Weigh K according to the stoichiometric ratio of 2 CO 3 , Na 2 CO 3 , Nb 2 O 5 , BaCO 3 , TiO 2 and Dy 2 O 3 raw materials. Finally, ceramic material 3 is obtained for powder X-ray diffraction (PXRD) and dielectric property tests. Using the same analysis method as in Example 1. The PXRD pattern of sample 3 is as shown in Figure 1 , and the dielectric property test results are as shown in Figure 4 .

[0051] Example 4: The preparation method of Example 4 is basically the same as that of Example 1. The main difference is that according to the chemical general formula of 0.75(K 0.85 Na 0.15 )NbO 3 -0.25BaTi 0.8 Dy 0.2 O 3 Weigh K according to the stoichiometric ratio of 2 CO 3 , Na 2 CO3 , Nb 2 O 5 , BaCO 3 , TiO 2 and Dy 2 O 3 raw materials. Finally, ceramic material 4 was obtained for powder X-ray diffraction (PXRD) and dielectric property tests. The same analysis method as in Example 1 was used. The PXRD pattern of sample 4 is as shown in Figure 1 and the dielectric property test results are as shown in Figure 5 .

[0052] Example 5: The preparation method of Example 5 was basically the same as that of Example 1, with the main difference being that according to the chemical formula of 0.9(K 0.75 Na 0.25 )NbO 3 -0.1BaTiO 3 stoichiometric ratio, K 2 CO 3 , Na 2 CO 3 , Nb 2 O 5 , BaCO 3 and TiO 2 raw materials were weighed. Finally, ceramic material 5 was obtained for powder X-ray diffraction (PXRD) and dielectric property tests. The same analysis method as in Example 1 was used. The PXRD pattern of sample 5 is as shown in Figure 1 and the dielectric property test results are as shown in Figure 6 .

[0053] The important data of the dielectric property tests of the samples in Examples 1-5 were summarized in Table 1 as shown below.

[0054] Table 1:

[0055] From the Figure 1 PXRD as shown, the ceramic materials prepared in Examples 1-5 had good crystallinity.

[0056] From the Figure 2 - 6 and the dielectric property test results as shown in Table 1, it can be seen that the dielectric constant values of the ceramic materials prepared in Examples 1 and 2 were between 1500 and 2000, which were relatively high as a whole, and the upward trend with temperature was relatively gentle. In the temperature range of the X9R standard (-55°C to 200°C), the dielectric constant remained relatively stable, with a change rate less than ±15%. The dielectric loss values of the two samples were between 0.02 and 0.05, which were generally very low, especially excellent in the low-temperature range.

[0057] The ceramic materials obtained in Example 1 and Example 2 were further observed by scanning electron microscopy, as Figure 7 and Figure 8 shown. The ceramic materials prepared in Example 1 and Example 2 had dense grain sintering and no obvious pores.

[0058] For the ceramic materials prepared in Example 3 and Example 4, in the temperature range of -55 °C to 200 °C, the change rate of the dielectric constant was relatively large (exceeding ±15% of the dielectric constant at 25 °C), which did not meet the application standard of X9R.

[0059] Example 5 was compared with the composition of Example 1 without doping Dy element. The obtained ceramic material had a large temperature change at 180 - 200 °C and a high dielectric loss, which also exceeded the application standard of X9R.

[0060] In summary, the two ceramic materials obtained in Example 1 and Example 2 had stable dielectric properties in a wide temperature range, met the application standard of X9R, and were very suitable for application scenarios that required consistent performance at various temperatures.

Claims

1. An X9R type MLCC ceramic material, characterized in that: Its general chemical formula is: (1-x)(K 0.85 Na 0.15 )NbO3-xBaTi 0.8 Dy 0.2 O3, where the value of x is 0.1≤x≤0.

2.

2. The X9R type MLCC ceramic material according to claim 1, characterized in that: The general chemical formula of the ceramic material is: 0.9(K 0.85 Na 0.15 )NbO3-0.1BaTi 0.8 Dy 0.2 O3; or 0.8(K 0.85 Na 0.15 )NbO3-0.2BaTi 0.8 Dy 0.2 O3.

3. A method for preparing an X9R type MLCC ceramic material, characterized in that: The method comprises the following steps: (1) according to the chemical formula (1-x)(K 0.85 Na 0.15 )NbO3-xBaTi 0.8 Dy 0.2 (1) The raw materials of K2CO3, Na2CO3, Nb2O5, BaCO3, TiO2 and Dy2O3 are weighed in a stoichiometric ratio of O3, wherein the value of x is 0.1≤x≤0.2, and the raw materials are pre-dried to obtain pre-dried raw materials; (2) The pre-dried raw materials, zirconium oxide balls and anhydrous ethanol are mixed, placed in a nylon jar, and ball-milled using a planetary ball mill to obtain a first slurry; (3) The first slurry is dried to obtain a mixed powder; then, it is calcined at high temperature, and after calcination, it is cooled to room temperature to obtain a first calcined powder; (4) The first calcined powder, zirconium oxide balls and anhydrous ethanol are mixed, placed in a nylon jar, and ball-milled twice using a planetary ball mill to obtain a second slurry; (5) The second slurry is dried, and it is sieved through a sieve to obtain a second calcined powder; (6) Polyvinyl alcohol is added to the second calcined powder for granulation, and finally granulated at 100-200 MPa pressure, pressing the granulated powder into a ceramic disc; (7) heating the ceramic disc to 600°C in an air atmosphere, keeping it warm for 4 hours to perform a binder removal treatment, and obtaining a ceramic disc green body; (8) sintering the ceramic disc green body at high temperature, cooling it to room temperature after sintering, and obtaining a sintered ceramic disc; (9) at room temperature, applying silver paste on the surface of the sintered ceramic disc, heating it to 600°C, keeping it warm for 1 hour, and then cooling it to room temperature to obtain the X9R type MLCC ceramic material.

4. The method for preparing the X9R type MLCC ceramic material according to claim 3, characterized in that: In step (1), the pre-drying temperature is 70-90° C., and the pre-drying time is 0.5-16 hours.

5. The method for preparing the X9R type MLCC ceramic material according to claim 3, characterized in that: In step (2), the weight ratio of the pre-dried raw material, zirconium oxide balls and anhydrous ethanol is 1: (8-12): (4-6); and / or, in step (4), the weight ratio of the first calcined powder, zirconium oxide balls and anhydrous ethanol is 1: (8-12): (4-6).

6. The method for preparing the X9R type MLCC ceramic material according to claim 3, characterized in that: In step (5), the drying temperature is 80-120° C., and the drying time is 8-16 hours.

7. The method for preparing the X9R type MLCC ceramic material according to claim 3, characterized in that: In step (5), the sieve is a 60-100 mesh sieve.

8. The method for preparing the X9R type MLCC ceramic material according to claim 3, characterized in that: The weight ratio of the second calcined powder to the polyvinyl alcohol is 1:(0.02-0.1).

9. The method for preparing the X9R type MLCC ceramic material according to claim 3, characterized in that: The weight ratio of the second calcined powder to the polyvinyl alcohol is 1: 0.03, 1:0.05 or 1:0.

07.

10. The method for preparing the X9R type MLCC ceramic material according to claim 3, characterized in that: In step (8), the temperature of the high temperature sintering is 1000-1300° C., and the time of the high temperature sintering is 3-5 hours.

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