Oxygen nonstoichiometry and thermodynamic quantities of Perovskite-Type La1- xSrxFeO3-δ(x=0.2, 0.5, 0.8)
March 10-14, 2019
In this work, the defect structure analysis of La1-xSrxFeO3-δ (x=0.2, 0.5, 0.8) was presented. Thermogravimetric measurements were performed to determine the change in oxygen nonstoichiometry (Δδ) with oxygen partial pressure (pO2) in 10-19 ≤ (pO2/atm) ≤ 0.21 and temperature in 750 ≤ (T/℃) ≤ 900 range. La1-xSrxFeO3-δ showed a clear electronic stoichiometric point around δ»3-x/2. The relative partial molar enthalpy (ho-hoo) and entropy (so-soo) of oxygen were calculated from δ-pO2-T relation by using Gibbs-Helmholtz equation. The negative sign of ho-hoo and so-soo indicated that the incorporation of oxygen was an exothermic process and showed that the experimentally observed variations in ho-hoo and so-soo with δ matched well with the statistical thermodynamic model proposed by Mizusaki. The defect diagram analysis showed that in n-type regime Fe2+ concentration varied with (pO2)-1/4 whereas in p-type regime Fe4+ concentration varied with (pO2)1/4.
 J. Mizusaki et al. J. Solid State Chem. 67 (1987) 1-8.
Hohan Bae, Jaewoon Hong, Sun-Ju Song, and Mathur Lakshya, "Oxygen nonstoichiometry and thermodynamic quantities of Perovskite-Type La1- xSrxFeO3-δ(x=0.2, 0.5, 0.8)" in "Nonstoichiometric Compounds VII", ECI Symposium Series, (2019). https://dc.engconfintl.org/nonstoichiometric_vii/11