Phase Equilibration in ZrO ₂ ‐Y ₂ O ₃ Alloys by Liquid‐Film Migration

Abstract

The tetragonal ( t ) and cubic ( c ) ZrO 2 solid solutions in two‐phase ZrO 2 ‐8 wt% Y 2 O 3 ceramics have low and high solute content, respectively. Annealing samples sintered at 1600°C between 700° and 1400°C requires a change in the volume fraction of the coexisting phases, as well as their equilibrium Y 2 O 3 content. The enrichment in Y 2 O 3 content of the c ‐ZrO 2 grains is accomplished by liquid‐film migration involving the ubiquitous silicate grain‐boundary phase, while the volume fraction of t ‐ZrO 2 increases by the nucleation and growth of cap‐shaped t ‐ZrO 2 lenses. The interfaces between the c ‐ZrO 2 matrix and the growing t ‐ZrO 2 lenses are semicoherent.