Silicon nitride ceramic having devitrified intergranular glass p

Details Silicon nitride ceramic having devitrified intergranular glass p Silicon nitride ceramic having devitrified intergranular glass p

1989-11-27

1992-07-07

Dixon, Jr., William R.

Compositions: ceramic

Ceramic compositions

Refractory

501 98, C04B 3558

Patent

active

051282879

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.

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