Structure-Property and Thermodynamic Relationships in Rare Earth (Y, Eu, Pr) Iridate Pyrochlores

ABSTRACT This study relates structure, properties and thermodynamics, through synthesis, characterization and heat of formation measurements of rare earth iridate pyrochlore (RE2Ir2O7; RE = Y, Eu, Pr) crystalline powders. The RE2Ir2O7 phases are synthesized by high temperature solid-state synthesis methods. X-ray diffraction and elemental analysis techniques are utilized to validate the synthesis and enable structural comparisons. Trends in the bond angles indicate deviations from the Y and Eu analogs for the Pr2Ir2O7 phase. High temperature oxide melt solution calorimetry is used to determine the heats of formation of each phase. Breaking the trend expected across the rare earth series, the enthalpy of formation for Pr2Ir2O7 is more exothermic than the anticipated from the Y and Eu analogs.