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J. Korean Ceram. Soc. > Volume 59(6); 2022 > Article
Journal of the Korean Ceramic Society 2022;59(6): 876-888.
doi: https://doi.org/10.1007/s43207-022-00237-6
Defect chemistry of p-type perovskite oxide La0.2Sr0.8FeO3-δ: a combined experimental and computational study
Hohan Bae1, Yonghun Shin2, Lakshya Mathur1, Donghwa Lee2, Sun-Ju Song1
1Ionics Lab, School of Materials Science and Engineering, Chonnam National University, 77, Yongbong-ro, Buk-gu, Gwang-Ju 500-757, Republic of Korea
2Department of Materials Science and Engineering, Pohang University Science and Technology, Pohang 37673, Republic of Korea
Correspondence  Donghwa Lee ,Email: donghwa96@postech.ac.kr
Sun-Ju Song ,Email: song@chonnam.ac.kr
Received: February 25, 2022; Revised: July 15, 2022   Accepted: July 24, 2022.  Published online: August 18, 2022.
In this study, the mass and charge transport properties of La0.2Sr0.8FeO3-δ have been investigated by deploying defect chemical analysis. From the thermo-gravimetric analysis and DC 4-probe method, oxygen non-stoichiometry (δ) and total electrical conductivity (σ) were examined as functions of temperature (750 < T/°C < 900) and partial pressure of oxygen (10–20 < Po2/atm < 0.21). The standard enthalpy and entropy changes of reactions and the defect concentrations were calculated from the defect chemical relation. Relative partial molar quantities of mixing of component oxygen were also calculated from both Gibbs–Helmholtz relation and the statistical thermodynamic model. The semiconductor-like conducting behavior due to the localized electrons/holes was observed as with the variation of δ . Electron/hole mobility and oxygen ion partial conductivity were also quantitatively extracted based on the defect structure. Furthermore, first-principles density functional theory (DFT) calculations predict oxidation in Po2 regime Po2 > 10–15 –10–12 atm (750–900 °C) can release extra holes and eventually increase electrical conductivity.
Key words: Oxgen Nonstoichiometry · First-principles density funtional theory (DFT) calculation · Defect structure · Electronic structure · Thermodynamic quantities
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