Slow crack growth behavior of two gas pressure sintered Si3N4 ceramics with
different additives; a Yb2Si2O7 composition and an Al2O3-Y2O3 composition,
was investigated by constant stress-rate ("dynamic fatigue") testing at 14
00 degreesC. The slow crack growth parameter. n, was 14.7 and 6.3 for Si3N4
With Yb2Si2O7 and Al2O3-Y2O3 compositions, respectively. Superior crack gr
owth resistance of Si3N4 with Yb2Si2O7 composition was due to its higher re
fractoriness of intergranular glassy films, compared to Si3N4 with Al2O3-Y2
O3 composition. (C) 2001 Elsevier Science Ltd. All rights reserved.