Effect of Ga2O3 on Sintering and Phase Stability of Sc2O3‐Doped Tetragonal Zirconia Prepared via Aqueous Solution Route

The effects of the presence of Ga₂O₃ on low‐temperature sintering and the phase stability of 4, 5, and 6 mol% Sc₂O₃‐doped tetragonal zirconia ceramics (4ScSZ, 5ScSZ, and 6ScSZ, respectively) were investigated. A series of zirconia sintered bodies with compositions (ZrO₂)_0.99?x(Sc₂O₃)_x(Ga₂O₃)_0.01, x = 0.04, 0.05, and 0.06 was fabricated by sintering at 1000°C to 1500°C for 1 h using fine powders that were prepared via the combination of homogeneous precipitation method and hydrolysis technique using monoclinic zirconia sols synthesized through the forced hydrolysis of an aqueous solution of zirconium oxychloride at 100°C for 168 h. The presence of 1 mol% Ga₂O₃ was effective in reducing sintering temperature necessary to fabricate dense bodies and enabled to obtain dense sintered bodies via sintering at 1100°C for 1 h. The phase stability, that is, low‐temperature degradation behavior of the resultant zirconia ceramics was determined under hydrothermal condition. The zirconia ceramics codoped with 1 mol% Ga₂O₃ and 6 mol% Sc₂O₃ (1Ga6ScZ) fabricated via sintering at 1300°C for 1 h showed high phase stability without the appearance of monoclinic zirconia phase, that is the tetragonal‐to‐monoclinic phase transformation was not observed in the 1Ga6ScZ after treatment under hydrothermal condition at 150°C for 30 h.