EFFECT OF DOPANT SPECIES ON TETRAGONAL (T')-TO-MONOCLINIC PHASE-TRANSFORMATION OF ARC-MELTED ZRO2-RO(1.5) (R=SM, Y, ER, AND SC) IN WATER AT200-DEGREES-C AND 100 MPA PRESSURE

Arc-melted specimens of rare-earth-doped zirconia (ZrO2-X mol% RO(1.5) ; X = 4-10 for R = Sm, Y,Er, and X = 4-18 for Sc) were hydrothermally treated at 200 degrees C, 100 MPa to investigate the dependence of the tetragonal-to-monoclinic transformation on dopant species and its con tent. The volume fraction of monoclinic phase VM(t) increased from Vm( 0) to a certain saturated value Vm(infinity), following [Vm(t) - Vm(0) ]/[Vm(t) - Vm(infinity)] = 1 - exp(-k . t), where t is the annealing t ime at 200 degrees C, 100 MPa. The transformabilities, Vm(0), Vm(infin ity), and k decrease with increasing dopant content. The Vm(infinity) decreased with an increase of ionic radius of dopants. The relation 0 < Vm(infinity) < 1 suggests that apparent noncompositional inhomogenei ty exists in the hydrothermally treated sample.