Growth and defect crystal structure of CdF2 and nonstoichiometric Cd1-xRxF2+x phases (R = Rare Earth and In). Part 3. Crystal structure of As-grown Cd0.90R0.10F2.10 (R = Sm-Lu, Y) single crystals

摘要

The structures of as-grown Cd0.90R0.10F2.10 (R = Sm-Lu and Y) crystals are determined and related to the CaF2 structure type. It is assumed that in all the crystals R3+ and Cd2+ ions form clusters with the tetrahedral configuration of the [Cd2R2F26] and [CdR3F26] cations. The concentration of [Cd2R2F26] cations in crystals with R = Er-Lu and Y is considerably higher that in crystals with R = Sm-Ho. The tendency to a decrease in the coordination number of R3+ toward the end of the rare earth series manifests itself in the fact that the Yb3+ ions in Cd0.90Yb0.10F2.10 occupy both tetrahedral (c.n. 10) and octahedral (c.n. 9) clusters. The Yb3+, ions in tetrahedral clusters are displaced from their basic positions by 0.15 angstrom along the < 100 > directions. In Cd1-xRxF2+x the relaxation of the anion sublattice of the fluorite matrix around clusters is much more pronounced than in the Ca1-xRxF2+x phases having similar geometry. (c) 2005 Pleiades Publishing, Inc.