Crystallite size-dependent phases in nanocrystalline ZrO2–Sc2O3

Abstract

ZrO₂-10, 12 and 14 mol% Sc₂O₃ nanopowders were prepared by using a nitrate-lysine gel-combustion synthesis. These materials were studied by synchrotron X-ray powder diffraction (SXPD) and Raman spectroscopy after calcination at different temperatures from 650 to 1200 °C, which led to samples with different average crystallite sizes, up to about 100 nm. The results from SXPD and Raman analyses indicate that, depending on Sc₂O₃ content, the metastable t′′-form of the tetragonal phase or the cubic phase are fully retained at room temperature in nanocrystalline powders, provided an average crystallite sizes lower than ∼30 nm. By contrast, powders with larger average crystallite sizes exhibit the stable rhombohedral, β and γ, phases and do not retain or very partially retain the metastable t′′ and cubic ones.