Electrochemical Determination of Gibbs Energy of Formation of LaCrO3 Using a Composition-Graded Bielectrolyte

Authors

  • Kallarackel Thomas Jacob,

    1. Department of Materials Engineering, Indian Institute of Science, Bangalore, India
    Search for more papers by this author
    • Emeritus Member, The American Ceramic Society.
  • Sapna Gupta,

    1. Department of Materials Science and Engineering, University of Connecticut, Storrs, Connecticut
    Search for more papers by this author
  • Prabhakar Singh

    Corresponding author
    1. Department of Materials Science and Engineering, University of Connecticut, Storrs, Connecticut
    • Department of Materials Engineering, Indian Institute of Science, Bangalore, India
    Search for more papers by this author
    • Fellow, The American Ceramic Society.

Author to whom correspondence should be addressed. e-mail: singh@engr.uconn.edu

Abstract

Presented are new measurements of the standard Gibbs free energy of formation of rhombohedral LaCrO3 from component oxides La2O3 and Cr2O3 in the temperature range from 875 to 1175 K, using a bielectrolyte solid-state cell incorporating single crystal CaF2 and composition-graded solid electrolyte (LaF3)y·(CaF2)1−y (= 0–0.32). The results can be represented analytically as math formula (±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 LaCrO3 from elements at 298.15 K computed from the results of this study is math formula/kJ·mol−1 = −1536.2 (±7). The standard entropy of orthorhombic LaCrO3 at 298.15 K is estimated as 99.0 (±4.5) J·(mol·K)−1.

Ancillary