Determination of oxygen nonstoichiometry in SrFeO3−δ by solid‐state Coulometric titration. Issue 6 (20th March 2017)

• Record Type: Journal Article
• Authors: Yoo, Jiho; Yoo, Chung‐Yul; Yu, Ji‐Haeng; Jacobson, Allan J.
• Is Part Of: Journal of the American Ceramic Society. Volume 100:Issue 6(2017)
• Page Start: 2690
• Page End: 2699
• Publication Date: 2017-03-20
• Subjects: Coulometric titration -- oxygen nonstoichiometry -- perovskite -- phase transition -- strontium iron oxide; Ceramics -- Periodicals; 620.1405
• DOI: 10.1111/jace.14755
• Languages: English
• ISSNs: 0002-7820

Abstract

Abstract: The oxygen nonstoichiometry of SrFeO3−δ was determined by solid‐state Coulometric titration at 750°C‐1040°C and 10 −18 ≤ p O2 (atm)≤0.5. At T ≤850°C, a hysteresis in the oxygen nonstoichiometry (δ) isotherms indicates the presence of a two‐phase region corresponding to a mixture of a perovskite and an oxygen vacancy ordered phase. The variation of δ with temperature at fixed p O2 values and the variation of log( p O2 ) with reciprocal temperature at fixed δ are reported. The p O2 at the p ‐ n transition in the electrical conductivity increases as the temperature increases, and the transition in the conductivity isotherm occurs at a composition of SrFeO2.505(1) at 950°C and SrFeO2.508(1) at 900°C. Since strontium exclusively occupies the A‐site, a simple point defect model that assumes noninteracting defects can describe the isotherms but only at 1040°C; nonideal behavior is observed at lower temperatures. The partial molar thermodynamic quantities for oxygen in SrFeO3−δ were determined.