Abstract
The dependencies of phase evolution and thermodynamic properties of Gd2Zr2O7 with temperature of preparation have been reported. A series of samples with composition Gd2Zr2O7 have been prepared. The effect of temperature on the phases has been inferred from the powder XRD and Raman spectroscopy. High temperature favors the formation of pyrochlore phase compared to the defect fluorite type phase. The evolution of phase was further quantitatively explained by measuring the formation energy employing high temperature calorimeter. The samples with predominantly pyrochlore phase have higher ΔfH°298 and thermodynamically stable. Also, it is observed that the pyrochlore type phase has larger formation energy compared to fluorite type phase and hence the fluorite to pyrochlore phase transformation is driven by enthalpy. On increasing the annealing temperature more disorder fluorite structure is formed and once the defect concentrations exceed a critical value they order to form the thermodynamically stable pyrochlore structure.
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