SEMICONDUCTOR CERAMIC POWDER, SEMICONDUCTOR CERAMIC, AND MONOLITHIC SEMICONDUCTOR CERAMIC CAPACITOR

• US 20100103587A1
• Filed: 12/22/2009
• Published: 04/29/2010
• Est. Priority Date: 06/27/2007
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: Kawamoto, Mitsutoshi
• Granted Patent: US 8,040,658 B2
• Time in Patent Office: Days
• US Class Current: 361/321.100
• CPC Class Codes: C01G 23/006 Alkaline earth titanates
• CPC Class Codes: C01P 2002/34 perovskite-type (ABO3)
• CPC Class Codes: C01P 2002/52 containing elements as dopants
• CPC Class Codes: C01P 2002/72 by d-values or two theta-values, e.g. as X-ray diagram
• CPC Class Codes: C01P 2004/61 Micrometer sized, i.e. from 1-100 micrometer
• CPC Class Codes: C01P 2004/62 Submicrometer sized, i.e. from 0.1-1 micrometer
• CPC Class Codes: C01P 2006/40 Electric properties
• CPC Class Codes: C04B 2235/3208 Calcium oxide or oxide-forming salts thereof, e.g. lime
• CPC Class Codes: C04B 2235/3224 Rare earth oxide or oxide forming salts thereof, e.g. scandium oxide
• CPC Class Codes: C04B 2235/3225 Yttrium oxide or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3227 Lanthanum oxide or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3229 Cerium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3241 Chromium oxides, chromates, or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3251 Niobium oxides, niobates, tantalum oxides, tantalates, or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3258 Tungsten oxides, tungstates, or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3267 MnO2
• CPC Class Codes: C04B 2235/3275 Cobalt oxides, cobaltates or cobaltites or oxide forming salts thereof, e.g. bismuth cobaltate, zinc cobaltite
• CPC Class Codes: C04B 2235/3279 Nickel oxides, nickalates, or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3281 Copper oxides, cuprates or oxide-forming salts thereof, e.g. CuO or Cu2O
• CPC Class Codes: C04B 2235/3418 Silicon oxide, silicic acids, or oxide forming salts thereof, e.g. silica sol, fused silica, silica fume, cristobalite, quartz or flint glass constituents C04B2235/36
• CPC Class Codes: C04B 2235/36 : Glass starting materials for making ceramics, e.g. silica glass
• CPC Class Codes: C04B 2235/449 : Organic acids, e.g. EDTA, citrate, acetate, oxalate
• CPC Class Codes: C04B 2235/5409 : expressed by specific surface values
• CPC Class Codes: C04B 2235/5445 : submicron sized, i.e. from 0,1 to 1 micron
• CPC Class Codes: C04B 2235/652 : Reduction treatment C04B2235/664 takes precedence
• CPC Class Codes: C04B 2235/6581 : Total pressure below 1 atmosphere, e.g. vacuum
• CPC Class Codes: C04B 2235/6582 : Hydrogen containing atmosphere
• CPC Class Codes: C04B 2235/6584 : at an oxygen percentage below that of air
• CPC Class Codes: C04B 2235/6588 : Water vapor containing atmospheres
• CPC Class Codes: C04B 2235/663 : Oxidative annealing
• CPC Class Codes: C04B 2235/785 : Submicron sized grains, i.e. from 0,1 to 1 micron
• CPC Class Codes: C04B 2235/79 : Non-stoichiometric products, e.g. perovskites (ABO3) with an A/B-ratio other than 1
• CPC Class Codes: C04B 2235/85 : Intergranular or grain boundary phases
• CPC Class Codes: C04B 35/47 : based on strontium titanates
• CPC Class Codes: C04B 35/62675 : characterised by the treatment temperature
• CPC Class Codes: C04B 35/62685 : characterised by the order of addition of constituents or additives
• CPC Class Codes: C04B 35/638 : Removal thereof
• CPC Class Codes: H01G 4/1227 : based on alkaline earth titanates
• CPC Class Codes: H01G 4/30 : Stacked capacitors H01G4/33 takes precedence
• CPC Class Codes: Y10T 428/2982 : Particulate matter [e.g., sphere, flake, etc.]

Abstract

A SrTiO₃-based grain boundary insulation type semiconductor ceramic contains a donor element in solid solution in crystal grains, an acceptor element at least in crystal grain boundaries, an integral width of (222) face of the crystal face of 0.500° or less, and an average powder grain size of crystal grains of 1.0 μm or less. A semiconductor ceramic is obtained by firing this ceramic, and a monolithic semiconductor ceramic capacitor is obtained by using the semiconductor ceramic. The SrTiO₃-based grain boundary insulation type semiconductor ceramic powder has a large apparent relative dielectric constant ∈r_APP of 5,000 or more even when the average ceramic grain size of crystal grains is 1.0 μm or less and which has an excellent insulating property. The monolithic semiconductor ceramic capacitor is capable of having a large capacity through reduction in thickness and multilayering.

Claims

1. A semiconductor ceramic powder which is a SrTiO₃-based grain boundary insulation type semiconductor ceramic powder containing a donor element as a solid solution in crystal grains and an acceptor element at least in crystal grain boundaries, wherein

the integral width of (222) face of the crystal face is 0.500°

or less, and

the average powder grain size of crystal grains is 1.0 μ

m or less.

2. The semiconductor ceramic powder according to claim 1, characterized in that the donor element comprises at least one element selected from the group consisting of La, Sm, Dy, Ho, Y, Nd, Ce, Nb, Ta, and W.

3. The semiconductor ceramic powder according to claim 2, characterized in that the acceptor element comprises at least one type of element selected from the group consisting of Mn, Co, Ni, and Cr.

4. The semiconductor ceramic powder according to claim 3, characterized in that the donor element is present in an amount of 2 mol or less relative to 100 mols of Ti site elements and the amount of acceptor element is present in an amount of 0.1 to 1 mol relative to 100 mols of Ti site elements.

5. The semiconductor ceramic powder according to claim 4, characterized in that the donor element is present in an amount of 1 mol or less relative to 100 mols of Ti site elements, and the ratio of Sr site elements to Ti site elements is 0.995 to 1.01.

6. The semiconductor ceramic powder according to claim 5, characterized in that the donor element is present in an amount of 0.8 to 1 mol or less relative to 100 mols of Ti site elements, the amount of acceptor element is present in an amount of 0.5 mol relative to 100 mols of Ti site elements, and the ratio of Sr site elements to Ti site elements is 1.00 to 1.01.

7. The semiconductor ceramic powder according to claim 1, characterized in that the acceptor element comprises at least one type of element selected from the group consisting of Mn, Co, Ni, and Cr.

8. A semiconductor ceramic which is a sintered semiconductor ceramic powder according to claim 7.

9. The semiconductor ceramic according to claim 8, characterized by having been sintering at a temperature lower than the calcination temperature of the semiconductor ceramic powder.

10. A monolithic semiconductor ceramic capacitor comprising internal electrodes disposed in a component element assembly and having external electrodes electrically connected to the internal electrodes and which are disposed on surfaces of the component element assembly,

wherein the component element assembly comprises a semiconductor ceramic according to claim 9.

11. A semiconductor ceramic which is a sintered semiconductor ceramic powder according to claim 6.

12. The semiconductor ceramic according to claim 11, characterized by having been sintering at a temperature lower than the calcination temperature of the semiconductor ceramic powder.

13. A monolithic semiconductor ceramic capacitor comprising internal electrodes disposed in a component element assembly and having external electrodes electrically connected to the internal electrodes and which are disposed on surfaces of the component element assembly,

wherein the component element assembly comprises a semiconductor ceramic according to claim 11.

14. A semiconductor ceramic which is a sintered semiconductor ceramic powder according to claim 2.

15. The semiconductor ceramic according to claim 14, characterized by having been sintering at a temperature lower than the calcination temperature of the semiconductor ceramic powder.

16. A monolithic semiconductor ceramic capacitor comprising internal electrodes disposed in a component element assembly and having external electrodes electrically connected to the internal electrodes and which are disposed on surfaces of the component element assembly,

wherein the component element assembly comprises a semiconductor ceramic according to claim 14.

17. A semiconductor ceramic which is a sintered semiconductor ceramic powder according to claim 1.

18. The semiconductor ceramic according to claim 17, characterized by having been sintering at a temperature lower than the calcination temperature of the semiconductor ceramic powder.

19. A monolithic semiconductor ceramic capacitor comprising internal electrodes disposed in a component element assembly and having external electrodes electrically connected to the internal electrodes and which are disposed on surfaces of the component element assembly,

wherein the component element assembly comprises a semiconductor ceramic according to claim 18.

20. A monolithic semiconductor ceramic capacitor comprising internal electrodes disposed in a component element assembly and having external electrodes electrically connected to the internal electrodes and which are disposed on surfaces of the component element assembly,

wherein the component element assembly comprises a semiconductor ceramic according to claim 17.