# US 5,700,419 A · Process for producing sintered ITO compact

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- Number: US 5,700,419 A
- Document ID: US5700419A
- Status: Granted
- Kind: A
- Application number: 08/745,625
- Filed: 1996-11-08
- Granted: 1997-12-23
- Earliest claimed: 1995-11-08
- Assignees: Tosoh Corporation
- Inventors: Osamu Matsunaga; Akio Kondo
- Web page: https://patentgrep.com/patent/US5700419A

## CPC

- C04B 35/457: based on tin oxides or stannates
- 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

## Abstract

A sintered ITO compact having an ultra-high density of at least 7.08 g/cm.sup.3 is produced by a process wherein an aqueous slurry comprised of indium oxide, tin oxide, a binder, a dispersant and an aqueous medium is cast in a mold, and the thus-obtained cast green body is sintered. The aqueous slurry used is prepared by the steps of: dispersing uniformly a tin oxide powder and a dispersant in an aqueous medium to give an aqueous slurry; allowing the aqueous slurry to stand whereby coarse particles of tin oxide are sedimented; separating by decantation an upper liquid layer of the aqueous slurry containing finely divided particles of tin oxide (preferably, the secondary particle sizes of which are not larger than 4 .mu.m) and the dispersant from a lower liquid layer containing the sedimented coarse particles; and then, incorporating an indium oxide powder and a binder in the separated upper liquid layer containing finely divided tin oxide particles and the dispersant to give an aqueous slurry.

## Claims

### Claim 1

A process for producing a sintered ITO compact wherein an aqueous slurry comprised of indium oxide, tin oxide, a binder, a dispersant and an aqueous medium is cast in a mold, and the thus-obtained cast green body is sintered; said aqueous slurry being prepared by the steps of:
dispersing uniformly a tin oxide powder and a dispersant in an aqueous medium to give an aqueous slurry;
allowing the aqueous slurry to stand whereby coarse particles of tin oxide are sedimented;
separating by decantation an upper liquid layer of the aqueous slurry containing finely divided particles of tin oxide and the dispersant from a lower liquid layer containing the sedimented coarse particles; and then,
incorporating an indium oxide powder and a binder in the separated upper liquid layer containing finely divided tin oxide particles and the dispersant to give an aqueous slurry.

### Claim 2 (depends on 1)

A process for producing a sintered ITO compact according to claim 1 wherein at least 70% by volume of the tin oxide powder to be dispersed in the aqueous medium is composed of secondary particles having a particle size of not larger than 1 .mu.m.

### Claim 3 (depends on 1)

A process for producing a sintered ITO compact according to claim 1 wherein the tin oxide powder is dispersed in 50 to 80% by weight, based on the weight of the tin oxide powder, of the aqueous medium.

### Claim 4 (depends on 1)

A process for producing a sintered ITO compact according to claim 1 wherein the aqueous slurry is allowed to stand for the sedimentation of coarse particles of tin oxide for a time sufficient for making not larger than 4 .mu.m the secondary particle size of the finely divided particles of tin oxide contained in the upper liquid layer of the aqueous slurry to be separated by decantation.

### Claim 5 (depends on 1)

A process for producing a sintered ITO compact according to claim 1 wherein the indium oxide powder to be incorporated in the separated upper liquid layer is a compacted powder having a tap density of 1.2 to 2.4 g/cm.sup.3.

### Claim 6 (depends on 1)

A process for producing a sintered ITO compact according to claim 1 wherein the amounts of the tin oxide powder and the indium oxide powder in the aqueous slurry to be cast in a mold are 5 to 15% by weight and 95 to 85% by weight, respectively, based on the total weight of the tin oxide powder and the indium oxide powder.

### Claim 7 (depends on 1)

A process for producing a sintered ITO compact according to claim 1 wherein the as-cast green body is dried and compacted by cold isostatic pressing at a pressure of at least 2 ton/cm.sup.2, the compacted green body is heated to a temperature of 300.degree. to 500.degree. C. at a heating rate of not higher than 5.degree. C./hr, the heated green body is subjected to a dewaxing treatment at that temperature, and then the treated green body is sintered.

### Claim 8 (depends on 1)

A process for producing a sintered ITO compact according to claim 1 wherein the sintering is effected at a temperature of 1,450.degree. to 1,550.degree. C. and an atmospheric pressure in an oxygen atmosphere.