SCANNING TUNNELING MICROSCOPE STUDY OF SURFACE RELIEF INDUCED BY THE TETRAGONAL-TO-MONOCLINIC TRANSFORMATION IN A ZIRCONIA-YTTRIA ALLOY

Surface relief induced by the tetragonal-to-monoclinic transformation in an arc-melted zirconia-yttria alloy has been investigated quantitatively, on a nanometer scale, with the scanning tunneling microscope. It was found by optical microscopy that two types of transformation products exist, the herringbone type and the acicular type. The surface relief of the herringbone and acicular products was successfully delineated by STM. The surface relief angles of the herringbone product were measured quantitatively, and they were in good agreement with results calculated from the phenomenological theory of martensitic transformation. Thus, STM was proved to be a useful tool for studying the surface relief resulting from a shear-type transformation, particularly when a quantitative measurement is needed for comparing the result with a predicted value from the phenomenological theory.