Stability of ZrO2–Y2O3t′ phase formed during laser sealing

Results are reported concerning the effect of thermal treatments in the temperature range 1050–1500°C for 1–1000 h on the stability of the t′ phase present in laser sealed layers of ZrO2–8·5 wt-% Y2O3. Aging for up to 1000 h at 1050°C is not sufficient to cause significant transformation of the t′ phase. At temperatures >1300°C, the t′ phase is less stable and transforms to mixtures of the t and c phases in proportions which are a function of both the time and temperature of aging. An improvement in the fracture toughness of the sealed layer was found to occur when substantial proportions of t phase were produced by annealing.MST/1529