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Impurity‐Enhanced Intergranular Cavity Formation in Silicon Nitride at High Temperatures
Author(s) -
Tanaka Isao,
Pezzotti Giuseppe,
Matsushita Kenichi,
Miyamoto Yoshinari,
Okamoto Taira
Publication year - 1991
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1991.tb06920.x
Subject(s) - impurity , intergranular corrosion , materials science , nucleation , silicon , silicon nitride , relaxation (psychology) , nitride , metallurgy , analytical chemistry (journal) , composite material , chemistry , microstructure , layer (electronics) , psychology , social psychology , organic chemistry , chromatography
The effect of trace impurities on high‐temperature strength is examined in Si 3 N 4 sintered without additives. Strength degradation above 1000°C occurs only in the low‐purity material, which also exhibits an intergranular slow crack growth (SCG) rate 2 orders of magnitude faster than that of the high‐purity material at 1400°C. A relaxation peak of internal friction is observed only in the low‐purity material, at ≅1200°C, and the origin of this peak is ascribed to the initial stage of SCG—that is, the cavity‐nucleation stage, enhanced by impurities. Based on the present results, a model for impurity‐enhanced SCG is proposed.