Water incorporation in tetragonal zirconia

Samples of 3 mol% Y2O3-stabilized tetragonal ZrO2 ceramics were annealed at 250degreesC in atmospheres of water vapor pressures of 1 bar and 26 mbar. As demonstrated by the water uptake and the lattice expansion, water molecules were incorporated into the ZrO2 lattice during annealing, and the amount of the incorporated water is determined by the water vapor pressure. Owing to the filling of oxygen vacancies by the incorporated water molecules, part of the tetragonal ZrO2 transformed to the monoclinic structure, and protonic defects were induced. The expected proton conduction was confirmed by the polarity of the water vapor concentration cells.