초록 ▼

Sintered silicon nitride-silica-yttria ceramic articles having silica-rich or yttria-rich casing layers are disclosed. The surface layers are formed by sintering pre-compacted bodies in a powder setter bed to produce unitary sintered bodies having surface layers in which the atom ratio of yttrium to

Sintered silicon nitride-silica-yttria ceramic articles having silica-rich or yttria-rich casing layers are disclosed. The surface layers are formed by sintering pre-compacted bodies in a powder setter bed to produce unitary sintered bodies having surface layers in which the atom ratio of yttrium to silicon has a smooth gradient from the surface of the article to the interior body of the article.

대표청구항 ▼

A unitary, sintered, polycrystalline silicon nitride based article including an interior body portion and a surface layer portion, said article comprising a major phase consisting essentially of silicon nitride and a minor phase consisting essentially of compounds of silicon, yttrium, nitrogen, and

A unitary, sintered, polycrystalline silicon nitride based article including an interior body portion and a surface layer portion, said article comprising a major phase consisting essentially of silicon nitride and a minor phase consisting essentially of compounds of silicon, yttrium, nitrogen, and oxygen wherein the atom ratio of yttrium to silicon in said minor phase of said surface layer portion of said article differs from the atom ratio of yttrium to silicon in said minor phase of said interior body portion of said article.