Metastable-stable phase diagrams in the zirconia-containing systems utilized in solid-oxide fuel cell application

Metastable-stable phase diagrams of ZrO2-RO(1.5) systems (R=Y, Sc and Er) are reviewed, noting the cation-diffusionless transformations and reasonable diagrams are proposed. A tetragonal phase with an axial ratio of unity is interpreted to appear in the compositional region around 16 mol.% YO1.5.