Growth and defect crystal structure of CdF2 and nonstoichiometric Cd1 − x R x F2+x phases (R = Rare Earth Elements and In). 2. Methods of structure refinement of Cd0.90R0.10F2.10 phases using the example of Cd0.90Tb0.10F2.10. Structure of nanodimensional clusters in Cd0.90 Tb0.10F2.10 crystal

Abstract

The structures of the CdF2 and Cd0.90Tb0.10F2.10 crystals, the first representatives of the family of nonstoichiometric CdF2-based Cd1 − x R x F2+x phases (R = La-Lu, Y), are determined by X-ray diffraction analysis. The structures belong to the CdF2 structure type. The nonstoichiometric CaF2 phases have structural defects—interstitial fluorine atoms and vacancies in the main anionic motif. The structural data allowed us to establish for the first time the simultaneous presence in Cd0.90Tb0.10F2.10 of two types of clusters—electrically neutral [CdTb3F26] and charged [Cd2Tb2F26] 1−—and to determine their structure. The cluster charge is compensated with the vacancies in the positions of the main fluorine atoms, which may give rise to superionic conductivity in Cd1-x R x F2+x crystals.