Oxygen nonstoichiometry and thermodynamic quantities of Perovskite-Type La1- xSrxFeO3-δ(x=0.2, 0.5, 0.8)

Conference Dates

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[1]. 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.


[1] J. Mizusaki et al. J. Solid State Chem. 67 (1987) 1-8.

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