PAC Characterization of Nontransformable Tetragonal t′ Phase in Arc-Melted Zirconia-2.8 mol% Yttria Ceramics

Abstract

Tetragonal compact bodies obtained by quenching from the melt a ZrO2-2.8 mol% Y2O3 commercial powder have been investigated between room temperature and 1150°C, using mainly perturbed angular correlations spectroscopy. The resulting nontransformable t′ phase observed by optical micrography is characterized at nanoscopic level by a hyperfine interaction describing defective and disordered Zr4+ neighborhoods very different from those of the regular tetragonal phase. A small amount of remaining Zr4+ sites corresponds to a scarcely distorted tetragonal structure. As the compacts are heated, two processes activate: the movement of vacancies and the gradual and irreversible conversion of t′ defective sites into less defective ones, probably resulting from oxygen absorption.