On the Conversion of Bulk Polycrystalline Y ₂ O ₃ into the Nanocrystalline State

Abstract

A reversible phase transformation (RPT) process is observed that converts fully dense polycrystalline Y 2 O 3 directly into the nanocrystalline state. The process involves a forward transformation from cubic‐to‐monoclinic symmetry under a high pressure and a reverse transformation from monoclinic‐to‐cubic symmetry under a lower pressure. An example is given of a reduction in grain size of cubic‐Y 2 O 3 from 300 to 0.1 μm in a single pressure‐induced RPT at 1000°C.