Phase relations in the system Sr-Cr-O and thermodynamic properties of SrCrO4 and Sr3Cr2O8

The phase relations involving various oxides in the system Sr-Cr-O at 1250 K have been determined by equilibrating samples representing 17 compositions inside the ternary and subsequent phase identification in quenched samples. Optical and SEM microscopy were used in conjunction with XRD to identify...

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Veröffentlicht in:Journal of Phase Equilibria 2000-02, Vol.21 (1), p.46-53
Hauptverfasser: JACOB, K. T, ABRAHAM, K. P
Format: Artikel
Sprache:eng
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Zusammenfassung:The phase relations involving various oxides in the system Sr-Cr-O at 1250 K have been determined by equilibrating samples representing 17 compositions inside the ternary and subsequent phase identification in quenched samples. Optical and SEM microscopy were used in conjunction with XRD to identify phases; the composition of each phase was verified using EDAX. Four stable ternary oxides, SrCrO4, Sr3Cr2O8, Sr2CrO4, and SrCr2O4, were identified. All the compounds except Sr3Cr2O8 were found to be stoichiometric within the accuracy of EDAX. X-ray absorption near-edge structure (XANES) analysis showed an average valence of Cr suggestive of the presence of mixed valence states in this compound. Only one of the ternary oxides, SrCr2O4, was found to coexist with Cr metal. The compounds SrCrO4 and Sr3Cr2O8 were stable in pure oxygen. The standard Gibbs energy of formation of SrCrO4 was determined as a function of temperature in the range from 950 to 1280 K using a solid-state cell incorporating single-crystal SrF2 as the electrolyte. The oxygen potential corresponding to the three-phase equilibria involving SrCrO4, Sr3Cr2O8, and Cr2O3 was measured from 1080 to 1380 K. The standard Gibbs energy of formation of Sr3Cr2O8 was derived from the oxygen potential. (Author)
ISSN:1054-9714
1547-7037
1544-1032
1863-7345
1934-7243
DOI:10.1361/105497100770340417