Phase stability and microstructure of manganese-doped calcia-stabilized zirconia heat treated in a reducing atmosphere

The effects of Mn3O4 addition and annealing under a reducing atmosphere (N2:H2=97:3) on the microstructure and phase stability of calcia-stabilized zirconia (CSZ) ceramics sintered at 1500 °C for 3 h in air were investigated. Undoped and Mn3O4-doped 12.5 mol% CSZ (125CSZ) ceramics were prepared via a conventional solid-state reaction process. X-ray diffraction patterns showed a single cubic phase of ZrO2 in 0.3 mol% Mn3O4-doped 125CSZ after sintering at 1500 °C for 3 h. Monoclinic ZrO2 phases were observed in 0.5 mol% Mn3O4-doped 125CSZ and undoped 15 mol% CSZ ceramic after annealing at 1300 °C for 30 cycles in a reducing atmosphere. The amount of monoclinic ZrO2 phase observed in 0.5 mol% Mn3O4-doped 125CSZ was less than that found in undoped 15 mol% CSZ annealed at 1300 °C under a reducing atmosphere.