Thermodynamic studies of CaLaFe11O19(s)

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 (ΔfG0m), enthalpy of formation and heat capacity (C0p, m) of the compound were calculated as a function of temperature for the first time.C0p, 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: ΔfH0m(298.15 K)/kJ mol−1=−6057(±8) and S0m(298.15 K)/J K−1 mol−1=427(±5). ΔfH0m(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 K to 1000 K for CaLaFe11O19(s) was also constructed to represent an optimized set of data.

graphical abstractVariation of standard molar heat capacities of CaLaFe11O19(s) and MFe12O19(s) (M=Sr, Ba and Pb) as a function of temperature.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Thermodynamic studies on CaLaFe11O19(s) were performed using KEQMS and solution calorimetry. ► It was synthesized using gel combustion route and characterized by XRD technique. ► The compound is magnetic in nature and shows a heat capacity anomaly at 684 K. ► Thermodynamic table was constructed from 298 K to 1000 K.