CONTROL OF THE TETGRAGONAL-TO-MONOCLINIC PHASE TRANSFORMATION OF YTTRIA-DOPED TETRAGONAL ZrO//2 POLYCRYSTALS BY ANNEALING IN WATER.

The tetragonal-to-monoclinic phase transformation of yttria-doped tetragonal ZrO//2 polycrystals by annealing in humid atmosphere and hot aqueous solutions at 80-600 degree C was studied. Three approaches, decreasing the grain size, dispersing 0-40 wt% Al//2O//3 and alloying ZrO//2(Y//2O//3) with 0-20 wt% CeO//2 were examined to control the tetragonal-to-monoclinic phase transformation. The amount of the monoclinic phase formed decreased with decreasing the grain size of ZrO//2 and with increasing the concentrations of dispersed Al//2O//3 and CeO//2 in solid solution.