Deformation of Monoclinic ZrO ₂ Polycrystals and Y ₂ O ₃ ‐Stabilized Tetragonal ZrO ₂ Polycrystals below the Monoclinic–Tetragonal Transition Temperature

Abstract

Ultrafine‐grained monoclinic ZrO 2 polycrystals (MZP) and 3‐mol%‐Y 2 O 3 ‐stabilized tetragonal ZrO 2 polycrystals (3Y‐TZP) were obtained by hot isostatic pressing (HIP). Both MZP and TZP were “high‐purity” materials with impurities less than 0.1 wt%. The deformation behavior was studied at 1373 K, which was lower than the monoclinic ↔ tetragonal transition temperature. The stress exponent of 3Y‐TZP with grain size of 63 nm was 3 in the higher stress region, and increased from 3 to 4 with decreasing stress. The deformation of MZP was characterized by a stress exponent of 2.5 over a wide stress range. The strain rate of 3Y‐TZP was slower than that of MZP by 1 order of magnitude. It was suggested that either the doped yttrium or the difference in the crystal structure affected the diffusion coefficients of ZrO 2 .