Ceramic composition, ceramic sintered body, capacitor and method for manufacturing the same

Abstract

The present invention provides a ceramic composition, comprising a primary mixture and a secondary mixture, wherein the primary mixture comprises a first primary ingredient powder and a second primary ingredient powder, and the first primary ingredient powder comprises BaTiO.sub.3, the second primary ingredient powder comprises any of SrTiO.sub.3, Ba.sub.0.95Ca.sub.0.05TiO.sub.3, BaZr.sub.0.1Ti.sub.0.9O.sub.3 or a combination thereof, and the secondary mixture comprises a rare earth oxide, a silicon oxide and an alkaline-earth metal oxide. The present invention further provides a ceramic sintered body obtained by sintering the ceramic composition, and a capacitor comprising the ceramic sintered body and a method for manufacturing the same; wherein the capacitor satisfies EIA-X8R specification, and has a high dielectric constant.

Claims

1. A ceramic composition, comprising a primary mixture and a secondary mixture, wherein the primary mixture comprises a first primary ingredient powder and a second primary ingredient powder; the first primary ingredient powder comprises BaTiO.sub.3; the second primary ingredient powder comprises any of SrTiO.sub.3, CaTiO.sub.3, BaZrO.sub.3, SrZrO.sub.3, BaxCa.sub.(1?x)TiO.sub.3, CaxSr.sub.(1?x)ZrO.sub.3, BaZryTi.sub.(1-y)O.sub.3, CaxSr.sub.(1?x)ZryTi.sub.(1-y)O.sub.3 or a combination thereof, wherein x is from 0.91 to 0.99, and y is from 0.05 to 0.2; and based on the total amount of the primary mixture, the first primary ingredient powder is in an amount of 55 weight percent to 95 weight percent, and the second primary ingredient powder is in an amount of 5 weight percent to 45 weight percent; and the secondary mixture comprises a rare earth oxide, a silicon oxide and an alkaline-earth metal oxide.

2. The ceramic composition as claimed in claim 1, wherein based on the primary mixture in an amount of 100 molar percent, the secondary mixture is in an amount of 1.1 molar percent to 13.5 molar percent.

3. The ceramic composition as claimed in claim 1, wherein based on the primary mixture in an amount of 100 molar percent, the rare earth oxide, the silicon oxide and the alkaline-earth metal oxide are in an amount of 0.3 molar percent to 8 molar percent: 0.01 molar percent to 1.5 molar percent: 0.1 molar percent to 5.5 molar percent.

4. The ceramic composition as claimed in claim 1, wherein the average particle diameter of the first primary ingredient powder is 150 nanometers to 600 nanometers.

5. The ceramic composition as claimed in claim 1, wherein the first primary ingredient powder is prepared by solid state reaction, oxalate coprecipitation or hydrothermal method.

6. The ceramic composition as claimed in claim 1, wherein the second primary ingredient powder comprises any of SrTiO.sub.3, Ba.sub.0.95Ca.sub.0.05TiO.sub.3, BaZr.sub.0.1Ti.sub.0.9O.sub.3 or a combination thereof.

7. The ceramic composition as claimed in claim 1, wherein the primary mixture further comprises a third primary ingredient powder, and the third primary ingredient powder is CaZrO.sub.3.

8. The ceramic composition as claimed in claim 7, wherein based on the total amount of the primary mixture, the first primary ingredient powder is in an amount of 45 weight percent to 75 weight percent, the second primary ingredient powder is in an amount of 15 weight percent to 25 weight percent, and the third primary ingredient powder is in an amount of 5 weight percent to 35 weight percent.

9. A ceramic sintered body, obtained by sintering the ceramic composition as claimed in claim 1, and comprising multiple granules connecting to each other; wherein the granules each have a core and a shell, and the shell is located at an outer surface of the core; wherein the core comprises a particle of the first primary ingredient powder or a particle of the second primary ingredient powder; and the shell comprises the rare earth oxide, the silicon oxide and the alkaline-earth metal oxide.

10. A ceramic sintered body, obtained by sintering the ceramic composition as claimed in claim 7, and comprising multiple granules connecting to each other; wherein the granules each have a core and a shell, and the shell is located at an outer surface of the core; wherein the core comprises a particle of the first primary ingredient powder, a particle of the second primary ingredient powder or a particle of the third primary ingredient powder; and the shell comprises the rare earth oxide, the silicon oxide and the alkaline-earth metal oxide.

11. A capacitor, comprising: a dielectric ceramic body, comprising multiple ceramic sintered bodies as claimed in claim 9 and multiple internal electrodes, and the ceramic sintered bodies and the internal electrodes are stacked up on each other to form the dielectric ceramic body; and two external electrodes, which are respectively disposed on two opposite sides of the dielectric ceramic body and are electrically connected to the internal electrodes.

12. The capacitor as claimed in claim 11, wherein the dielectric constant of the capacitor is 1200 or more.

13. The capacitor as claimed in claim 11, which satisfies EIA-X8R specification or EIA-X9R specification, wherein EIA-X8R specification requires a capacitance variation of ?15% between ?55? C. and +150? C., and EIA-X9R specification requires a capacitance variation of ?15% between ?55? C. and +200? C.

14. The capacitor as claimed in claim 12, which satisfies EIA-X8R specification or EIA-X9R specification, wherein EIA-X8R specification requires a capacitance variation of ?15% between ?55? C. and +150? C., and EIA-X9R specification requires a capacitance variation of ?15% between ?55? C. and +200? C.

15. A capacitor, comprising: a dielectric ceramic body, comprising multiple ceramic sintered bodies as claimed in claim 10 and multiple internal electrodes, and the ceramic sintered bodies and the internal electrodes are stacked up on each other to form the dielectric ceramic body; and two external electrodes, which are respectively disposed on two opposite sides of the dielectric ceramic body and are electrically connected to the internal electrodes.

16. The capacitor as claimed in claim 15, wherein the dielectric constant of the capacitor is 1200 or more.

17. The capacitor as claimed in claim 15, which satisfies EIA-X8R specification or EIA-X9R specification, wherein EIA-X8R specification requires a capacitance variation of ?15% between ?55? C. and +150? C., and EIA-X9R specification requires a capacitance variation of ?15% between ?55? C. and +200? C.

18. The capacitor as claimed in claim 16, which satisfies EIA-X8R specification or EIA-X9R specification, wherein EIA-X8R specification requires a capacitance variation of ?15% between ?55? C. and +150? C., and EIA-X9R specification requires a capacitance variation of ?15% between ?55? C. and +200? C.

19. A method for manufacturing capacitors, comprising: mixing the ceramic composition as claimed in claim 1 and a first solvent to obtain a ceramic slurry; casting the ceramic slurry to obtain a ceramic foil; disposing an internal electrode on one surface of the ceramic foil to obtain a ceramic foil with the internal electrode; stacking up multiple said ceramic foils with the internal electrode on each other to obtain a laminated ceramic body; sintering the laminated ceramic body to obtain a dielectric ceramic body, wherein the dielectric ceramic body has a laminated structure formed by stacking up multiple ceramic sintered bodies and multiple internal electrodes on each other, wherein the multiple ceramic sintered bodies each are formed by sintering the ceramic foil; and disposing an external electrode on each of two opposite sides of the dielectric ceramic body to obtain the capacitor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 provides a schematic sectional view of the capacitor of the present invention.

(2) FIG. 2 provides a schematic sectional view of the core and the shell of the ceramic sintered body of the present invention.

(3) FIG. 3 is an electron microscopy photo showing a sectional view of the ceramic sintered body of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(4) The present invention is further explained through the following embodiments. A person having ordinary skill in the art can easily understand the advantages and efficacies achieved by the present invention. The present invention should not be limited to the contents of the embodiments. A person having ordinary skill in the art can make some improvement or modifications which are not departing from the spirit and scope of the present invention to practice or apply the content of the present invention.

(5) Preparation 1: Capacitors

(6) The manufacturing methods of all examples in the present invention were the same, as described as follows. A mixture of ethanol and toluene was served as a first solvent for the following use. The first solvent was added into 100 moles of a primary mixture powder to obtain a preliminary mixture. The preliminary mixture was added with a commercial dispersant, and then mixed evenly by a bead mill to obtain a primary mixture slurry. In addition, the first solvent was also added into a secondary mixture powder, and then mixed evenly by a bead mill to obtain a secondary mixture slurry. The primary mixture slurry and the secondary mixture slurry were mixed, added with a commercial organic binder of polyvinyl butyral (PVB) and then mixed evenly by a bead mill to obtain a ceramic slurry. The ceramic slurry was cast on a polyester film (as a carrier, not included in the ceramic foil herein) by a tape casting coater to obtain a ceramic foil with a thickness of 10 microns. An internal electrode of nickel was printed on the surface of the ceramic foil by screen or gravure printing to obtain a ceramic foil with the internal electrode. The ceramic foils with the internal electrode were stacked up on each other to obtain a laminated ceramic body, wherein a ceramic foil which did not comprise any internal electrode was disposed on the top and at the bottom of the laminated ceramic body, thus the ceramic foils were served as the top layer and the bottom layer of the laminated ceramic body. The laminated ceramic body was cut into appropriate size and heated at 250? C. to 350? C. for 12 hours to 36 hours in the nitrogen atmosphere to burn out organic substances, and then sintered in a reducing atmosphere comprising hydrogen and nitrogen for 18 minutes to 32 minutes at a temperature of 1200? C. to 1320? C. to obtain a dielectric ceramic body. The dielectric ceramic body was subjected to a tumbling treatment, and two opposite side surfaces thereof were stained (or dipped) with a copper paste, and then the dielectric ceramic body stained with the copper liquid was heated at 750? C. to 900? C. in an atmosphere of nitrogen to gain a copper electrode layer on each of the two opposite side surfaces, each of the copper electrode layers was further electroplated to form a nickel layer and a tin layer sequentially to form an external electrode, and a capacitor was obtained.

(7) As shown in FIG. 1, a capacitor 1 comprises: a dielectric ceramic body 10, comprising multiple ceramic sintered bodies 100 and multiple internal electrodes 110, and the ceramic sintered bodies 100 and the internal electrodes 110 are stacked up on each other (or alternately stacked up) to form the dielectric ceramic body 10; and two external electrodes 11, which are respectively disposed on opposite side surfaces 120 of the dielectric ceramic body 10 and are electrically connected to the internal electrodes 110.

(8) As shown in FIG. 2, the ceramic sintered body 100, which is obtained by sintering the ceramic composition, comprises multiple granules 1000 connecting to each other; wherein the granules 1000 each have a core 1001 and a shell 1002, and the shell 1002 is located at an outer surface of the core 1001; wherein the core 1001 comprises a particle of the first primary ingredient powder or a particle of the second primary ingredient powder, and the shell 1002 comprises the rare earth oxide, the silicon oxide and the alkaline-earth metal oxide. Besides, the cores 1001 did not directly contact each other.

(9) FIG. 3 is a microstructure photo of the ceramic sintered body, wherein 1003 is BaTiO.sub.3; 1004 is Ba.sub.0.95Ca.sub.0.05TiO.sub.3; and 1005 is CaZrO.sub.3.

(10) Test for capacitors: dielectric constant, dissipation factor and temperature coefficient of capacitance

(11) A capacitance meter (Model AGILENT4278A) was adopted to measure the capacitance and dissipation factor (DF) of the capacitor under a frequency of 1 KHz and an Alternating Current (AC) voltage of 1 Vrms. The temperature coefficient of capacitance (TCC) represented as ?C/C was also measured under the frequency of 1 KHz and the AC voltage of 1 Vrms based on the capacitance change ratio at operating and reference temperature, wherein the reference temperature is 25? C.

(12) The dielectric constant is calculated by the formula: C=?*?.sub.0*A/d; wherein C is capacitance (unit: F); ? is the dielectric constant of the dielectric layer (i.e., K value); ?.sub.0 is vacuum permittivity constant (8.86?10.sup.?12) (unit: F/m); A is plate area of the capacitor (unit: m.sup.2); d is the thickness of the dielectric layer (unit: m). The capacitor of the present invention adopts the imperial system of 0805 specification and the actual size is 2.00 mm?1.25 mm.

Example 1-1 to Example 1-6

(13) The manufacturing methods for Example 1-1 to Example 1-6 were the same as Preparation 1. The ceramic compositions and the test results of the dielectric constant, dissipation factor (DF) and the temperature coefficient of capacitance (TCC) of Example 1-1 to Example 1-6 were shown in Table 1. Further, when a multilayer ceramic capacitor satisfies EIA-X8R specification, the ceramic composition thereof was marked as O.

(14) According to Table 1, based on the total amount of the primary mixture, when the first primary ingredient powder was in an amount of 60 weight percent to 90 weight percent, the second primary ingredient powder was in an amount of 10 weight percent to 40 weight percent; and the primary mixture was in an amount of 100 molar percent, the rare earth oxide was in an amount of 2 molar percent to 4 molar percent, the silicon oxide was in an amount of 0.2 molar percent to 1 molar percent, and the alkaline-earth metal oxide was in an amount of 1 molar percent to 5 molar percent, the capacitors thereof satisfied EIA-X8R specification. Besides, each of the examples had a dielectric constant higher than 2600, and a DF between 2.4 and 6.8%.

(15) Besides, a silicon oxide and an alkaline-earth metal oxide were generally used for adjusting the properties of the laminated ceramic sintered body. Therefore, according to the comparisons among Example 1-2, Example 1-4 and Example 1-6, the addition amounts of the silicon oxide and alkaline-earth metal oxide were not high, and the impacts on the capacitance change thereof were not high, either.

Example 1-1, Example 1-2, and Example 2-1 to Example 2-13

(16) The manufacturing methods for Example 1-1, Example 1-2, and Example 2-1 to Example 2-13 were the same as Preparation 1. The ceramic compositions and the test results of the dielectric constant, dissipation factor (DF) and the temperature coefficient of capacitance (TCC) thereof were shown in Table 2. Further, when a multilayer ceramic capacitor satisfies EIA-X8R specification, the ceramic composition thereof was marked as O.

(17) According to the comparison between Example 1-1 and Example 2-1 in Table 2, and that between Example 1-2 and Example 2-8, when the ceramic composition was further added with a third primary ingredient powder, the dissipation factor of the capacitor reduced by half. Therefore, the addition of the third primary ingredient powder facilitated the improvement of the dissipation factor of the capacitor.

(18) Second, according to the comparisons among Example 2-4 to Example 2-7, increasing the amount of a rare earth oxide can improve the dissipation factor of the capacitor with no or slight impact on the capacitance change.

(19) Finally, according to the comparisons among Example 2-8 to Example 2-10, and Example 2-11 to Example 2-13, when the second primary ingredient powder is Ba.sub.0.95Ca.sub.0.05TiO.sub.3, or the second primary ingredient powder is BaZr.sub.0.1Ti.sub.0.9O.sub.3, increasing the amount of the third primary ingredient powder can reduce the capacitance change as well.

Example 1-2, and Example 3-1 to Example 3-3

(20) The manufacturing methods for Example 1-2 and Example 3-1 to Example 3-3 were the same as Preparation 1; wherein the ceramic compositions of Example 3-1 to Example 3-3 were the same as that of Example 1-2, except the average particle diameters of the first primary ingredient powders thereof were different. The average particle diameters of the first primary ingredient powders and the test results of the capacitor dielectric constant, dissipation factor (DF) and the temperature coefficient of capacitance (TCC) of all examples were shown in Table 3.

(21) According to Table 3, when the average particle diameters of the first primary ingredient powders were 200 nanometers to 500 nanometers, the capacitor can satisfy EIA-X8R specification.

(22) According to Example 1-2, when the average particle diameter of the first primary ingredient powder was 400 nanometers, the multilayer ceramic capacitor had the lowest capacitance change, which was between ?10%.

(23) To sum up, the second primary ingredient powder comprising SrTiO.sub.3, Ba.sub.0.95Ca.sub.0.05TiO.sub.3 or BaZr.sub.0.1Ti.sub.0.9O.sub.3 can make the capacitor satisfy EIA-X8R specification. Besides, the addition of CaZrO.sub.3 in the ceramic composition can improve the dissipation factor of the capacitor and reduce the capacitance change. Finally, controlling the average particle diameters of the first primary ingredient powder also facilitates the reduction of the capacitance change.

(24) TABLE-US-00001 TABLE 1 The ceramic compositions and the test results of the capacitors of Example 1-1 to Example 1-6 First Second primary primary Rare earth Silicon Alkaline-earth ingredient ingredient oxide oxide metal oxide Di- (wt %) (wt %) (mol %) (mol %) (mol %) electric DF TCC (%) EIA- Ingredients BaTiO.sub.3 SrTiO.sub.3 Ba.sub.0.95Ca.sub.0.05TiO.sub.3 Y.sub.2O.sub.3 Yb.sub.2O.sub.3 SiO.sub.2 BaO MgO constant (%) ?55? C. 150? C. X8R Example 1-1 90 10 4 0.5 1 3028 2.4 ?13 ?15 O Example 1-2 70 30 2 0.5 1 3023 5.2 ?8 ?9 O Example 1-3 60 40 2 0.5 1 2997 6.8 ?10 2 O Example 1-4 70 30 2 0.2 1 2669 4.9 ?5 ?7 O Example 1-5 70 30 2 0.8 1 3189 5.9 ?11 ?12 O Example 1-6 70 30 2 1 5 3028 6.2 ?15 ?12 O

(25) TABLE-US-00002 TABLE 2 The ceramic compositions and the test results of the capacitors of Example 1-1, Example 1-2, and Example 2-1 to Example 2-13 First Third pri- Second pri- Sili- mary primary mary con Di- ingre- ingredient ingre- Rare earth oxide Alkaline-earth elec- TCC dient (wt %) dient oxide (mol metal oxide tric (%) Ingre- (wt %) Ba.sub.0.95Ca.sub.0.05 BaZr.sub.0.1 (wt %) (mol %) %) (mol %) con- DF ?55? 150? EIA- dients BaTiO.sub.3 SrTiO.sub.3 TiO.sub.3 Ti.sub.0.9O.sub.3 CaZrO.sub.3 Y.sub.2O.sub.3 Yb.sub.2O.sub.3 Dy.sub.2O.sub.3 SiO.sub.2 BaO MgO CaO stant (%) C. C. X8R Exam- 90 10 0 4 1 0.5 1 3028 2.4 ?13 ?15 O ple 1-1 Exam- 70 20 10 4 0.5 1 1427 1.2 ?5 ?14 O ple 2-1 Exam- 60 20 20 4 0.5 1 1218 1.0 ?3 ?12 O ple 2-2 Exam- 50 20 30 4 0.5 1 973 0.9 1 ?4 O ple 2-3 Exam- 70 20 10 0.5 0.5 1 2133 1.7 0 ?15 O ple 2-4 Exam- 70 20 10 1 0.5 1 1572 1.4 ?2 ?15 O ple 2-5 Exam- 70 20 10 2 0.5 1 1216 1.2 ?4 ?14 O ple 2-6 Exam- 70 20 10 6 0.5 1 1194 1.0 ?9 ?12 O ple 2-7 Exam- 70 30 0 2 0.5 1 3023 5.2 ?8 ?9 O ple 1-2 Exam- 70 20 10 2 0.5 1 2618 2.6 ?10 ?14 O ple 2-8 Exam- 60 20 20 2 0.5 1 2371 2.1 ?8 ?13 O ple 2-9 Exam- 50 20 30 2 0.5 1 2003 1.7 ?6 ?11 O ple 2-10 Exam- 70 20 10 3 0.5 1 3452 2.9 ?7 ?15 O ple 2-11 Exam- 60 20 20 3 0.5 1 2817 2.5 ?6 ?14 O ple 2-12 Exam- 50 20 30 3 0.5 1 2204 2.4 ?3 ?12 O ple 2-13

(26) TABLE-US-00003 TABLE 3 The average particle diameters and the test results of the capacitors of Example 1-2, and Example 3-1 to Example 3-3 The average particle diameter of the first Di- primary ingredient electric TCC(%) EIA- powder (nanometers) constant DF(%) ?55? C. 150? C. X8R Example 500 3416 5.5 ?5 ?15 0 3-1 Example 400 3023 5.2 ?8 ?9 0 1-2 Example 300 2533 5.7 ?12 ?1 0 3-2 Example 200 2238 4.9 ?14 2 0 3-3