Annealing effect on phase stability of doped zirconia using experimental and computational studies
Abstract The effects of annealing at 600 °C and 800 °C up to 2000 h on the phase stabilities of doped stabilized zirconia, (Zr 0.85 Y 0.15 )O 2 − δ (8YSZ) and (Zr 0.81 Sc 0.18 Ce 0.01 )O 2 − δ (10SSZ), were investigated by Rietveld refinements with synchrotron X-ray diffraction (SR–XRD) and first-principle density functional theory (DFT) calculations. No marked change in the SR–XRD patterns was observed for the annealed samples of 8YSZ, and the amount of Y 2 O 3 phases was less than 0.01 mol% as estimated by comparison of the observed and simulated patterns in the annealed 8YSZ samples. Whereas the CeO 2 phase was visible in the SR–XRD patterns of the annealed 10SSZ samples, the peaks of the mother doped zirconia host structure did not change, and other phases were not detected. The CeO 2 content (under 0.12 mol%) was estimated quantitatively from the Rietveld refinements. Furthermore, the phase separations from the doped zirconia to the oxides, viz. , Y 2 O 3 ,Sc 2 O 3 , and CeO 2 , were investigated by the molar solution energy ( ΔE sol. ) calculated using the DFT calculations. ΔE sol. for the phase separation to each oxide indicated that the CeO 2 phase in 10SSZ would form more easily than the Y 2 O 3 and Sc 2 O 3 phases in 8YSZ and 10SSZ.