Silicon nitride ceramic and a process for its preparation
US5188781A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Oct 7, 1991 |
| Grant date | Feb 23, 1993 |
| Priority date | — |
| Expiry date | Oct 7, 2011 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC04B35/5935
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
A process for the preparation of an Si.sub.3 N.sub.4 ceramic of high strength, wherein .alpha.-Si.sub.3 N.sub.4 powder is mixed with small amounts of at least one of the elements La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho and Y in form of an oxide or oxide precursor, the mixture is shaped to a shaped body and the shaped body is sintered under pressures of 1-100 bar in a nitrogen atmosphere at temperatures of 1,750.degree.-2,000.degree. C. is described. The sintered body is heated at temperatures of 1200.degree.-1500.degree. C. in an inert gas atmosphere for at least 10 hours and then cooled. During this procedure, crystalline apatites of the formula A.sub.4+x (SiO.sub.4).sub.3 N.sub.x, A denoting the element added in the form of the oxide or oxide precursor and x denoting a number which is greater than zero and not more than 1.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.