Temperature and Composition Dependence of the Cation Distribution in Synthetic ZnFeyAl2-yO4 (0 ≤ y ≤ 1) Spinels
✍ Scribed by J.C. Waerenborgh; M.O. Figueiredo; J.M.P. Cabral; L.C.J. Pereira
- Publisher
- Elsevier Science
- Year
- 1994
- Tongue
- English
- Weight
- 476 KB
- Volume
- 111
- Category
- Article
- ISSN
- 0022-4596
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✦ Synopsis
Members of the spinel solid solution series (\mathrm{ZnFe}{y} \mathrm{Al}{2-y} \mathrm{O}_{4}(y=) (0,0.2,0.4,0.6,1.0,1.5), and 2 ) were synthesized by direct solid state reaction of the simple metal oxides in air at (1400 \mathrm{~K}). Two aliquots of the single-phase spinels obtained for each composition were annealed at 1350 and (1000 \mathrm{~K}) for (48 \mathrm{hr}) and then quenched in water.
The structural study of the quenched samples was performed by powder XRD, using the Rictveld method of structure refinement. The inversion degrees estimated for (\mathrm{ZnFe}{2} \mathrm{O}{4}) up to (1350 \mathrm{~K}) are in good agreement with those published by O'Neill (Eur. (J). Mineral. 4, 571 (1992)) in the range (773-1223 \mathrm{~K}). The nonlinear enthalpy of disordering model of O'Neill and Navrotsky ( (A m). Mineral. 68, 181 (1983); Am. Mineral. 69, 733 (1984)), recently applied to several studies of simple spinel oxides, could successfully describe the cation arrangement in spinels of the binary solid solution series prepared in this work, with parameters (\alpha_{\mathrm{Zn-Al}}=+82) (\mathrm{kJ} \mathrm{mole}{ }^{-1}, \alpha_{\mathrm{Zn}-\mathrm{Fe}^{3}}=+46 \mathrm{~kJ} \mathrm{~mole}^{-1}, \beta=-20 \mathrm{~kJ} \mathrm{~mole}^{-1}), and (\boldsymbol{\sigma}=\mathbf{0}).
({ }^{57} \mathrm{Fe}) Mössbauer spectra collected at 300 and (80 \mathrm{~K}) consisted of only one doublet. Although the contribution of tetrahedral (\mathrm{Fe}^{3+}) could not be resolved, the variation of the estimated average hyperfine parameters with composition and quenching temperature could be correlated with the cation arrangement deduced from XRD data. O 1994 Academic Press, Inc.