Structural features of new rare earth-based mixed anions (O, S, F) compounds: relationships between optical absorption and rare earth environment
Language
en
Article de revue
This item was published in
Solid State Sciences. 2002, vol. 4, n° 11-12, p. 1471-1479
Elsevier
English Abstract
In the structure of α-LnSF and Ln2AF4S2 (A=Ca, Sr) compounds which can be considered as formed of layer stacking, the rare earth and fluorine atoms form [Ln2F2]4+ or [Ln2AF4]4+ fluorite-type blocks which alternate with ...Read more >
In the structure of α-LnSF and Ln2AF4S2 (A=Ca, Sr) compounds which can be considered as formed of layer stacking, the rare earth and fluorine atoms form [Ln2F2]4+ or [Ln2AF4]4+ fluorite-type blocks which alternate with double [S2]4− layers along the c-axis. Then, it appears possible to modify the size of the fluorite-type block without any modification of its charge. In the case of rare earth oxyfluorosulfides, two new classes of compounds Ln3OF3S2 (Ln=La, Ce) and La2O1.5FS were identified. The structures of these compounds are related to α-LnSF and Ln2O2S networks. In these frameworks, the charge of the blocks containing the rare earth ions can be 2+ or 4+. These blocks alternate with single or double layers of sulfur atoms. The local geometry (number of neighbors, bond distances and angles) around the rare earth varies as a function of the number of the sulfur sheets. Absorption properties in UV-visible range are correlated with the structural features.Read less <
English Keywords
Electronic transitions
UV-visible absorption
Structure refinement
Rare earth
Fluorosulfides
Oxyfluorosulfides
Powder X-ray/neutron diffraction
Origin
Hal imported