Energetics of formation of KFGdF3 binary-intermediate compounds

Abstract

Abstract Enthalpies of formation were measured for KGdF 4 , K 2 GdF 5 and KGd 2 F 7 using the transposed temperature drop calorimetry method. These compounds were synthesized by conventional solid state reaction methods using mixtures of KF and GdF 3 . The measured enthalpies of formation from fluorides for KGdF 4 , K 2 GdF 5 and KGd 2 F 7 were − 22.3, − 16.1 and − 18.3 kJ mol −1 , respectively. From these measurements, enthalpies of formation from the elements were computed to be − 2290.0, − 2852.4 and − 3985.2 kJ mol −1 for the respective compounds. These enthalpies were compared with estimated values calculated by two methods previously reported to be effective for multicomponent oxides. Estimated values compare favorably with measured data, with deviations ranging from 0.5 to 2.9%. The errors of 0.5–2.9% correspond to a 16–85 kJ mol −1 uncertainty range for Δ f H 0 of ternary fluorides from binary fluorides. One of these methods, based on the summation of Δ f H 0 values for the constituent binary fluorides, is recommended for the KGdF compounds.