Thermodynamic studies of CaLaFe₁₁O₁₉(s)

Abstract

Thermodynamic studies on CaLaFe₁₁O₁₉(s) were carried out using Knudsen effusion mass spectrometry and calorimetry, viz. differential scanning calorimetry and high temperature oxide melt solution calorimetry. Standard molar Gibbs free energy of formation (Δ_fG^o_m), enthalpy of formation and heat capacity (C^o_{p, m}) of the compound were calculated as a function of temperature for the first time.

C^o_{p, m}(CaLaFe₁₁O₁₉) was determined and used for second law analysis, from which enthalpy and entropy of formation of the compound were calculated and the respective values are: Δ_fH⁰_m(298.15 K)/kJ·mol⁻¹=−6057(±8) and S⁰_m(298.15 K)/J·K⁻¹·mol⁻¹=427(±5). Δ_fH⁰_m(298.15 K)/kJ·mol⁻¹: −6055(±6) was also calculated using oxide melt solution calorimetry, which is in close agreement with the second law value. A heat capacity anomaly was also observed at T=684 K. A table of thermodynamic data from 298.15 to 1000 K for CaLaFe₁₁O₁₉(s) was also constructed to represent an optimized set of data.

graphical abstract