Crystallization And Grain Growth Behavior Of La2O3-doped Yttria-stabilized Zirconia

The effect of La2O3 addition on the microstructure and grain growth behavior of yttria-stabilized zirconia (8YSZ) was investigated. To this end, 8YSZ was doped with 1–15 wt% La2O3 by means of colloidal processing, and then sintered at 1550 °C for 1 h. XRD results identified a dissolution limit of 5 wt% La2O3 in 8YSZ, the insoluble La2O3 at higher concentrations reacting with ZrO2 during sintering to form a secondary La2Zr2O7 phase. Both undoped and La2O3-doped 8YSZ specimens were annealed at 1400, 1500, and 1600 °C for 10, 50, and 100 h to induce grain growth. Grain growth measurement results showed that an increase in annealing temperature and holding time caused to grain growth in all specimens. Excessive grain growth was observed in the case of the undoped, and 1-5 wt% La2O3-doped 8YSZ specimens; however, the grain growth in 10 and 15 wt% La2O3-doped 8YSZ was inhibited by the formation of a pyrochloric La2Zr2O7 secondary phase around the grains and grain boundaries of 8YSZ. Grain gr