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Electrochemical Determination of Gibbs Energy of Formation of LaCrO 3 Using a Composition‐Graded Bielectrolyte
Author(s) -
Jacob Kallarackel Thomas,
Gupta Sapna,
Singh Prabhakar
Publication year - 2013
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/jace.12435
Subject(s) - orthorhombic crystal system , gibbs free energy , enthalpy , electrochemistry , standard enthalpy change of formation , materials science , thermodynamics , analytical chemistry (journal) , crystallography , chemistry , crystal structure , mineralogy , physics , electrode , chromatography
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 Δ G f ( ox )O(±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 Δ H f ( 298.15 )O/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 .