FORMATION OF METASTABLE T'-PHASE IN SOLUTE-REDISTRIBUTED Y-PSZ

Owing to solute redistribution by a liquid phase analogue of diffusion-induced grain-boundary migration metastable and anti-phase domain boundary-bearing tetragonal (t') phase was seen to occur in the cubic (c) matrix grain of sintered (1400-degrees-C, 2 h) and furnace-cooled yttria-partially stabilized zirconia (Y-PSZ) specimens (TZ3Y + 12Y-PSZ in molar ratios of 4:1, 1:1 and 1:4). In contrast to that formed by rapid by cooling, t'-phase formed by slow cooling shows no deformation accommodation twins. Subsequent ageing at 1100-degrees-C for up to 240 h caused the formation of finely tweed (c) and tetragonal (t) assemblages at the expense of coarse tweed t'-phase in the 12Y-PSZ grains. The absence of secondary deformation twins in the t'-phase formed by slow cooling is discussed.