# US 7,744,954 B2 · Method of producing a powder, powder, and multilayered ceramic capacitor using the same

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- Number: US 7,744,954 B2
- Document ID: US7744954B2
- Status: Granted
- Kind: B2
- Application number: 11/384,508
- Filed: 2006-03-21
- Published: 2006-09-28
- Granted: 2010-06-29
- Earliest claimed: 2005-03-22
- Assignees: TDK Corporation
- Inventors: Yoshinori Fujikawa; Satoko Ueda; Kouji Tokita
- Web page: https://patentgrep.com/patent/US7744954B2

## CPC

- C04B 35/4682: {based on BaTiO3 perovskite phase}
- C04B 35/47: based on strontium titanates
- C04B 35/62821: {Titanium oxide}
- C04B 35/62886: {by wet chemical techniques}
- C04B 38/009: {Porous or hollow ceramic granular materials, e.g. microballoons (C04B18/027, C04B20/002 take precedence)}
- H01G 4/1209: {characterised by the ceramic dielectric material (H01G4/1272, H01G4/1281 take precedence)}
- H01G 4/1218: {based on titanium oxides or titanates (H01G4/1245 takes precedence)}
- C04B 2111/00405: {Materials with a gradually increasing or decreasing concentration of ingredients or property from one layer to another}
- C04B 2111/00844: {for electronic applications}
- C04B 2235/3213: Strontium oxides or oxide-forming salts thereof
- C04B 2235/3215: Barium oxides or oxide-forming salts thereof
- C04B 2235/3224: Rare earth oxide or oxide forming salts thereof, e.g. scandium oxide
- C04B 2235/3225: Yttrium oxide or oxide-forming salts thereof
- C04B 2235/3232: Titanium oxides or titanates, e.g. rutile or anatase
- C04B 2235/3236: Alkaline earth titanates
- C04B 2235/96: Properties of ceramic products, e.g. mechanical properties such as strength, toughness, wear resistance
- H01G 4/30: Stacked capacitors (H01G4/33 takes precedence)
- Y10T 428/2991: Coated
- C04B: LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE {(roofing granules E04D7/005)}; CERAMICS (devitrified glass-ceramics C03C10/00); REFRACTORIES; TREATMENT OF NATURAL STONE
- H01G: CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE (selection of specified materials as dielectric H01B3/00; capacitors having potential barriers H10D1/62, H10K10/10)
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

A core/shell structured powder different in composition between the inside the particle and the surface thereof before sintering, so that it is possible to sinter the powder at lower temperature and give a core/shell structured powder having a shell portion uniform in thickness after sintering; a multilayered ceramic capacitor having a longer lifetime, by preparing the multilayered ceramic capacitor by using a powder having a core/shell structure different in composition between the inside the particle and the surface thereof before sintering; and a method of producing a powder by synthesizing particles in the liquid containing a raw material, wherein particles different in composition at least between the inside the particle and the surface thereof are obtained by adding a composition to be incorporated as a component of the particles to the liquid during the synthetic process so that the composition of the liquid changes continuously or intermittently.

## Claims

### Claim 1

A method of producing a powder comprising synthesizing particles in a liquid comprising raw materials of two or more elements,
wherein particles different in composition at least between the inside the particle and the surface thereof are obtained by supplying a composition (1) to be incorporated as a component of the particles to the liquid so that the composition of the liquid changes continuously or intermittently during the synthetic process, wherein
the obtained particles are oxides having a perovskite structure,
the oxide having a perovskite structure is an oxide represented by ABO3, A represents at least one element selected from the group A consisting of barium, strontium, lead, rare-earth metals, magnesium, potassium, and sodium, and B represents at least one element selected from the group B consisting of titanium, zirconium, and niobium,
at least a raw material comprising group-A element A1 and a raw material comprising group-B element B1 are incorporated in the liquid in advance before initiation of synthesis,
the composition (1) comprises a raw material comprising another group-A element A2 different from the A1 element, and
the raw material comprising element A1 and the raw material comprising element B1 are reacted and thereafter the composition (1) is supplied to the liquid and reacted in the synthesis process, and
the particles having a composition of A1B1O3 comprising the A1 and B1 elements as the principal components inside the particle and a composition of A2B1O3 comprising the A2 and B1 elements as the principal components in the surface of the particle are obtained.

### Claim 2 (depends on 1)

The method of producing a powder according to claim 1,
wherein the particles are synthesized by hydrothermal reaction.

### Claim 3 (depends on 2)

The method of producing a powder according to claim 2,
wherein the particles are synthesized in an alkaline solution at 80° C. or higher.

### Claim 4 (depends on 1)

The method of producing a powder according to claim 1, wherein composition (1) is supplied continuously.

### Claim 5 (depends on 1)

The method of producing a powder according to claim 1, wherein composition (1) is supplied intermittently.

### Claim 6 (depends on 1)

The method of producing a powder according to claim 1, wherein composition (1) is supplied continuously and intermittently in combination.

### Claim 7 (depends on 1)

The method of producing a powder according to claim 1, wherein A1 is barium, B1 is titanium, and A2 is strontium.