Method of producing sintered silicon nitride
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United States of America Patent
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Dec 7, 1999
Grant Date -
N/A
app pub date -
Jun 10, 1998
filing date -
Dec 12, 1995
priority date (Note) -
Expired
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Abstract
By providing a new method of producing sintered silicon nitride, this invention takes into account the fact that parts made of Si.sub.3 N.sub.4 are often used in temperature ranges below 1200.degree. C. and sometimes even below 500.degree. C. and therefore needn't be designed to withstand temperatures above 1200.degree. C. The sintered silicon nitride for these low-temperature applications is obtained by sintering silicon nitride powder of <2 .mu.m with 5 to 20 wt. % of one or more glass components of the same particle size at temperatures below 1400.degree. C. It is a prerequisite that the glass components used, preferably alkali metal borate glasses with a coefficient of thermal expansion .alpha. which matches that of Si.sub.3 N.sub.4, have a transformation point T.sub.g which is below 750.degree. C., and that the individual glass components have a free enthalpy .DELTA.G which is at least 60% of the free enthalpy of SiO.sub.2. For low-temperature applications, Si.sub.3 N.sub.4 parts manufactured cost-effectively in this way fully satisfy the demands made on them in respect of density, strength and .beta.-phase proportion.
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