Kinetics and Crystallography of the Monoclinic (B) to Cubic (C) Transformation in Dysprosia (Dy2O3)

Abstract

The large volume change (≈8%) and the fast kinetics of the monoclinic (B) to cubic (C) transformation at 1950°C in dysprosia (Dy2O3) causes shattering of ceramic bodies on cooling. This behavior is analogous to that of zirconia with its tetragonal (t) to monoclinic (m) transformation. Dysprosia was thus considered as a potential transformation toughener for high temperature applications. A laser-melting/roller-quenching technique was used to stabilize the high temperature monoclinic phase down to room temperature. The kinetics of the transformation back to the cubic phase through annealing heat treatments was followed by TGA, X-ray diffraction and electron microscopy techniques. A crystallographic model involving a shear mechanism was proposed.