Phase transformation and microstructure in (Mg,Ti)-PSZ

Abstract

Phase transformation and microstructure in Mg-PSZ (8 mol% MgO), sintered (1600°C, 6 h) with 0 to 15 mol% additions of TiO2 (designated as 0T to 15T specimens), were studied by X-ray diffraction and electron microscopy. According to the room-temperature X-ray lattice parameter, the saturation of TiO2 in the cubic (c-) zirconia was reached at a total TiO2 addition of ca. 6 mol% at 1600°C, whereas the solubility limit in tetragonal (t-) zirconia was not reached in the composition range studied. The amount of t-zirconia increases with increasing TiO2 content at 1600°C, as indicated by the monoclinic (m-) zirconia content in the furnace-cooled specimens. Regardless of the modification of the lattice misfit strain by TiO2 dissolution, the precipitates of t-phase in the c-matrix remain lenticular with {1 0 0} habit plane. Loops, due probably to condensation of the structural vacancies, were found in the m-phase of 9T, but not in 1T and 6T specimens.