Exaggerated Grain Growth in ZrO 2 ‐Toughened Al 2 O 3

Annealing of ZrO 2 ‐toughened Al 2 O 3 (ZTA) at elevated temperatures causes growth of both the intergranular ZrO 2 particles and the Al 2 O 3 “matrix” grains. Exaggerated (“breakaway”) grain growth occurs in some, but not all, specimens. Analytical electron microscopy of two ZTA's, both of which contained a continuous amorphous (glassy) grain‐boundary phase, but only one of which showed breakaway grain growth, revealed that the occurrence of breakaway grain growth could be correlated with the chemistry of the ubiquitous glassy grain‐boundary phase.