Structural Study on the Cubic to Tetragonal Transformation in Arc-melted ZrO₂-3 mol%Y₂O₃

A herringbone structure observed in an as arc-melted specimen was investigated using XRD, TEM and surface relief study. The specimen was cooled on a water cooled copper hearth and the grain size was approximately 1 mm. The results confirmed the crystal structure to be tetragonal (at=0.5100 and ct=0.5166 nm, c⁄a=1.0129). The orientation relation among the different variants of the tetragonal lattice and their arrangement in the herring bone structure were determined; the structure was shown to be suited for accommodation to the cubic (fluorite structure) to tetragonal transformation strain. Surface relief associated with the transformation was also observed and correlated to the transformation strain. From these results, the transformation was suggested to be of diffusionless type (martensitic).