Raman spectra of lanthanide sesquioxide single crystals: Correlation between A and B-type structures |
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Authors: | J Gouteron D Michel AM Lejus J Zarembowitch |
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Institution: | 1. Laboratoire de Spectrométrie Vibrationnelle L.A. 161, Ecole Nationale Supérieure de Chimie de Paris, 11, rue P. et M. Curie 75231 Paris Cédex 05 France;2. Laboratoire de Chimie Appliquée de l''Etat Solide L.A. 302, Ecole Nationale Supérieure de Chimie de Paris, 11, rue P. et M. Curie 75231 Paris Cédex 05 France |
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Abstract: | Structures and Raman spectra of lanthanide sesquioxide single crystals with A-type trigonal structure (La2O3, Pr2O3, Nd2O3, Sm2O3) and B-type monoclinic structure (Sm2O3, Eu2O3, Gd2O3) are compared. The B form (C32h or ) derives from the A form (D33d or ) by a slight lattice deformation, implying a splitting of D3d and C3v atomic positions into less symmetrical C2h and Cs sites. This close structural relationship allows one to relate the Raman active modes of the B-type crystals to vibrations of the A-type crystals and to deduce an interpretation of the complex B-type spectra from those of the simpler A-type spectra. Furthermore, it is shown that the frequency of the modes which mainly involve metal-oxygen stretching motion increases with the lanthanide atomic number in the A and B series. This evolution is interpreted in terms of increasing compactness of the structure. |
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Keywords: | Author to whom correspondence should be addressed |
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