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Serier-Brault, H., Thibault, L., Legrain, M., Deniard, P., Rocquefelte, X., Leone, P., Perillon, J.-L., Le Bris, S., Waku, J. & Jobic, S. (2014) Thermochromism in Yttrium Iron Garnet Compounds. Inorg. Chem. 53 12378–12383. 
Added by: Laurent Cournède (2016-03-10 21:01:54)
Type de référence: Article
DOI: 10.1021/ic501708b
Numéro d'identification (ISBN etc.): 0020-1669
Clé BibTeX: SerierBrault2014
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Catégories: MIOPS
Mots-clés: behavior, ions, optical-properties, Oxides, phase-transition, spectra, temperature, y3fe5o12
Créateurs: Deniard, Jobic, Le Bris, Legrain, Leone, Perillon, Rocquefelte, Serier-Brault, Thibault, Waku
Collection: Inorg. Chem.
Consultations : 14/568
Indice de consultation : 3%
Indice de popularité : 0.75%
Résumé     
Polycrystalline yttrium iron garnet (Y3Fe5O12, hereafter labeled YIG) has been synthesized by solid-state reaction, characterized by X-ray diffraction, Mossbauer spectroscopy, and UV-vis-NIR diffuse reflectance spectroscopy, and its optical properties from room temperature (RT) to 300 similar to C are discussed. Namely, its greenish color at RT is assigned to an O2- ? Fe3+ ligand-to-metal charge transfer at 2.57 eV coupled with d-d transitions peaking at 1.35 and 2.04 eV. When the temperature is raised, YIG displays a marked thermochromic effect; i.e., the color changes continuously from greenish to brownish, which offers opportunities for potential application as a temperature indicator for everyday uses. The origin of the observed thermochromism is assigned to a gradual red shift of the ligand-to-metal charge transfer with temperature while the positioning in energy of the d-d transitions is almost unaltered. Attempts to achieve more saturated colors via doping (e.g., Al3+, Ga3+, Mn3+ ...) remained unsuccessful except for chromium. Indeed, Y3Fe5O12:Cr samples exhibit at RT the same color than the undoped garnet at 200 similar to C. The introduction of Cr3+ ions strongly impacts the color of the Y3Fe5O12 parent either by an inductive effect or, more probably, by a direct effect on the electronic structure of the undoped material with formation of a midgap state.
Added by: Laurent Cournède  
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