STABLE AND METASTABLE PHASE-RELATIONSHIPS IN THE SYSTEM ZRO2-ERO1.5

Stable and metastable phase relationships in the system ZrO2-ErO1.5 were investigated using homogeneous samples prepared by rapid quenching of melts and by arc melting. The rapidly quenched samples were annealed in air for 48 h at 1690-degrees-C or for 8 months at 1315-degrees-C. Two tetragonal phases (t- and t'-phases) were observed after quenching samples heated at 1690-degrees-C to a room temperature, whereas one t-phase and cubic (c-) phase were found in those treated at 1315-degrees-C. Since the t'-phase is obtained through a diffusionless transformation during cooling from a high-temperature c-phase, t- and c-phases can coexist at high temperature. The t-and c-phases field spans from 4 to 10 mol% ErO1.5 at 1690-degrees-C and from 3 to 15 mol% ErO1.5 at 1315-degrees-C. The equilibrium temperature T0t-m between the t- and monoclinic (m-) phases estimated from A(s) and M(s) temperatures decreased with increasing ErO1.5 contents.