Silicon nitride ceramic having devitrified intergranular glass phase and a process for its preparation
US5128287A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Nov 27, 1989 |
| Grant date | Jul 7, 1992 |
| Priority date | — |
| Expiry date | Nov 27, 2009 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC04B35/584
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
The invention relates to a silicon nitride ceramic having a high strength both at low temperatures and at temperatures above 1000.degree. C., and to a process for its preparation. The silicon nitride ceramic contains, as the primary phase, .beta.-silicon nitride and, as a crystalline secondary phase, an yttrium compound which has been caused to crystallize out from the intergranular glass phase by thermal after-treatment. Teh yttrium-containing, crystalline secondary phase has the following d-values in an X-ray diffraction pattern using Cu-K.alpha. radiation: 4.69 .circle.; 4.05 .circle.; 3.48 .circle.; 3.20 .circle.; 3.06 .circle.; 2.81 .circle.; 2.40 .circle.; 2.07 .circle.; 2.03 .circle.; and 1.87 .circle., the most intense diffraction reflection having the d-value 3.06 .circle..+-.0.01 .circle.. A residue of amorphous glass phase is present in the ceramic as a further phase between the crystal grains.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.