Hydrothermal Ageing of Copper Oxide Doped Alumina Toughened Zirconia

This study investigates the hydrothermal aging behavior of undoped and copper oxide-doped alumina-toughened zirconia (ATZ). The ATZ ceramic composites underwent conventional sintering at temperatures ranging from 1250 to 1500 ℃ with a holding time of 12 min. XRD analysis revealed a stable 100% tetragonal phase for sintered ATZ samples up to 1450 ℃, even after 100 h of exposure. At 1500℃, XRD patterns of both undoped and doped ATZ samples showed no phase transformation after up to 3 h of exposure to superheated steam. Extended exposure, however, resulted in phase transformation beyond 10 h. CuO-doped ATZ samples initially exhibited lower monoclinic content, gradually increasing with aging. Undoped ATZ demonstrated better aging resistance, maintaining ~ 40% monoclinic content after 100 h. FESEM images post aging revealed surface roughness changes due to the tetragonal-to-monoclinic phase transformation, with limited nucleation in the largest tetragonal grains. Fracture analysis exhibited macrocracks and microcracks on the transformed surface layer after aging. This study found that 0.2wt% CuO doping did not prevent the low-temperature degradation (LTD) phenomenon at elevated temperature.