Silicon nitride type sintered bodies and method for producing the same
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United States of America Patent
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Mar 3, 1992
Grant Date -
N/A
app pub date -
Mar 2, 1990
filing date -
Jul 8, 1988
priority date (Note) -
Expired
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Abstract
The deterioration of strength at high temperature of Si.sub.3 N.sub.4 --Y.sub.2 O.sub.3 --AlN series silicon nitride-type sintered bodies is reduced by employing Y.sub.2 O.sub.3 --MgO--AlN series as a sintering aid wherein the stoichiometrical ratio of Y, Mg and Al in the sintered body is controlled to a specific range, thereby decreasing the glass phase to decrease deterioration of strength at high temperatures. Assuming Y as A.sub.1 mol, Mg as B.sub.1 mol and A.sub.1 as C.sub.1 mol based on one mol of Si.sub.3 N.sub.4 in the sintered body, the specific range, wherein each of A.sub.1, B.sub.1 and C.sub.1 is not less than 0, satisifies the conditions: ##EQU1## and the crystal phase of Si.sub.3 N.sub.4 consisting of an .alpha.-Si.sub.3 N.sub.4 phase in which a part of Si.sub.3 N.sub.4 is replaced by Y, Mg, O and Al, and a .beta.-Si.sub.3 N.sub.4 phase in which a part of Si.sub.3 N.sub.4 is replaced by Al and O, and a balance of a binding glass phase comprising Si, Al, O, N, Y and MG, wherein the ratio between the .alpha.-Si.sub.3 N.sub.4 phase and .beta.-Si.sub.3 N.sub.4 phase is defined as: ##EQU2##
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