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Systematics of Phase Transition and Mixing Energetics in Rare Earth, Yttrium, and Scandium Stabilized Zirconia and Hafnia
Author(s) -
Simoncic Petra,
Navrotsky Alexandra
Publication year - 2007
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2007.01678.x
Subject(s) - yttrium , hafnia , enthalpy , differential scanning calorimetry , endothermic process , scandium , exothermic reaction , chemistry , standard enthalpy of formation , oxide , calorimetry , cubic zirconia , materials science , inorganic chemistry , thermodynamics , adsorption , organic chemistry , ceramic , physics
Energetics of rare earth, yttrium, and scandium stabilized zirconia and hafnia have been systematically investigated by oxide melt solution calorimetry. The enthalpies of formation with respect to the oxide end members were simultaneously fit to a quadratic function to extract interaction parameters and enthalpies of transition of the oxide end members to the fluorite structure. ZrO 2 –SmO 1.5 and HfO 2 –SmO 1.5 show the most exothermic enthalpies of formation and interaction parameters, whereas ZrO 2 –ScO 1.5 has the least exothermic enthalpy of formation and interaction parameter. This suggests that the ZrO 2 –ScO 1.5 system shows the least short range order among all investigated systems, consistent with its high ionic conductivity. The extrapolated enthalpy of transition of the rare earth oxide end members to the cubic fluorite structure increase to more endothermic values with decreasing cation size. The γ‐cubic fluorite phase transition in ZrO 2 –ScO 1.5 was investigated by differential scanning calorimetry (DSC). The phase transition is reversible, occurs at 1000°–1200°C and shows hysteresis (∼100°C). The enthalpy of transition is endothermic on heating and increases from 1.7±0.1 kJ/mol (22 mol% ScO 1.5 ) to 2.9±0.2 kJ/mol (30 mol% ScO 1.5 ).