Vacuum process for avoiding devitrification damage to transparent slip-cast silica crucibles
US4072489A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 10, 1976 |
| Grant date | Feb 7, 1978 |
| Priority date | — |
| Expiry date | May 10, 1996 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S65/13
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
A process is disclosed for making vitreous silica crucibles of exceptional high quality for use in the growing of a silicon crystal from molten silicon. The crucibles are formed from fine particles of high purity fused silica by slip casting or other suitable process, are dried and fired to provide a rigid porous body, and are thereafter sintered to a high density, preferably to the transparent state. The invention solves the problem of spalling, blistering and cracking during crystal growing and the resulting contamination of the molten silicon, which has long plagued the industry, by eliminating water from the fused silica particles before the porous body is sintered to the transparent state. Said body is thoroughly dried in a vacuum furnace at a high temperature and at a sub-atmospheric pressure low enough to remove the chemically bound water which cannot be removed by heat alone. The crucibles of this invention retain their transparency and high quality without spalling or introducing microscopic particles of silica into the silicon, thereby making it possible to grow a silicon crystal of highest quality without dislocations and imperfections due to contamination by said partic…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.