Raman spectra of lanthanide sesquioxide single crystals: Correlation between A and B-type structures
Abstract
Structures and Raman spectra of lanthanide sesquioxide single crystals with A-type trigonal structure (La 2O 3, Pr 2O 3, Nd 2O 3, Sm 2O 3) and B-type monoclinic structure (Sm 2O 3, Eu 2O 3, Gd 2O 3) are compared. The B form ( C32 h or {C2}/{m}, Z = 6 ) derives from the A form ( D33 d or P overline3m1, Z = 1 ) by a slight lattice deformation, implying a splitting of D3 d and C3 v atomic positions into less symmetrical C2 h 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.
- Publication:
-
Journal of Solid State Chemistry France
- Pub Date:
- July 1981
- DOI:
- 10.1016/0022-4596(81)90058-X
- Bibcode:
- 1981JSSCh..38..288G