Electrochemical Determination of Gibbs Energy of Formation of LaCrO 3 Using a Composition‐Graded Bielectrolyte

Presented are new measurements of the standard Gibbs free energy of formation of rhombohedral LaCrO 3 from component oxides La 2 O 3 and Cr 2 O 3 in the temperature range from 875 to 1175 K, using a bielectrolyte solid‐state cell incorporating single crystal CaF 2 and composition‐graded solid electrolyte ( LaF 3 ) y ·( CaF 2 ) 1− y ( y = 0–0.32). The results can be represented analytically as (±2270)/J·mol −1 = −72329 + 4.932 ( T /K). The measurements were undertaken to resolve serious discrepancies in the data reported in the literature. A critical analysis of previous electrochemical measurements indicates several deficiencies that have been rectified in this study. The enthalpy of formation obtained in this study is consistent with calorimetric data. The standard enthalpy of formation of orthorhombic LaCrO 3 from elements at 298.15 K computed from the results of this study is /kJ·mol −1 = −1536.2 (±7). The standard entropy of orthorhombic LaCrO 3 at 298.15 K is estimated as 99.0 (±4.5) J·(mol·K) −1 .