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Determination of oxygen nonstoichiometry in SrFeO 3−δ by solid‐state Coulometric titration
Author(s) -
Yoo Jiho,
Yoo ChungYul,
Yu JiHaeng,
Jacobson Allan J.
Publication year - 2017
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.14755
Subject(s) - oxygen , coulometry , chemistry , analytical chemistry (journal) , perovskite (structure) , titration , electrical resistivity and conductivity , iodometry , conductivity , hysteresis , phase transition , strontium , phase (matter) , thermodynamics , crystallography , inorganic chemistry , electrochemistry , chromatography , physics , organic chemistry , electrode , quantum mechanics , electrical engineering , engineering
The oxygen nonstoichiometry of SrFeO 3−δ was determined by solid‐state Coulometric titration at 750°C‐1040°C and 10 −18 ≤ p O 2 (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 O 2 values and the variation of log( p O 2 ) with reciprocal temperature at fixed δ are reported. The p O 2 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 SrFeO 2.505(1) at 950°C and SrFeO 2.508(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 SrFeO 3−δ were determined.