Room-Temperature Degradation oft-Zr(Pr)O₂in an Aqueous Suspension Revealed by Perturbed Angular Correlations

This paper deals with the phase stability of an aqueous suspension of tetragonal Zr0.9Pr0.1O2 (20 wt%/vol%) at room temperature as a function of the aging time. The suspension is investigated in situ using the highly localized Perturbed Angular Correlations technique. The results indicate that an almost fully reversible degradation process toward monoclinic zirconia takes place through a first-order reaction of rate constant k = 0.7 day(-1). Two successive diffusion mechanisms are observed that are interpreted as OH- ions' migration in the grain surface and then, as proton defects' diffusion into the bulk.