| Abstract: | Relations between the structure and electrical properties of fluoride systems with different structures are presented. Physical properties of fluorite-structured (MF2-RF3, MF2-AF, MF2-M′F2, M = Ba, Pb, R = La-Lu, Sc, Y, A = Li, Na, K, Rb, M′ = Ba, Cd, Mg), orthorhombic (RF3, R = Tb-Er, Y), tysonite-structured (RF3-MF2, R = La-Nd, M = Sr), and monoclinic (BaR2F8, R = Ho-Yb, Y) fluoride single crystals or ceramics (ErF3, MF2-RF3, M = Ca, Ba, R = La, Gd, Tb, Y), glasses (ZBLAN, PIBAL) and eutectic composites (LiF-RF3, R = La-Gd, Y, PbF2-RF3, R = Ho, Yb, Y, Sc, PbF2-AF, A = Li, Na, PbF2-MgF2) are compared. Anisotropy of electrical properties is explained. Models of aggregation of defects into clusters are proposed. In fluoritestructured crystals, the highest ionic conductivity was found for PbF2: 7 mol % ScF3 (at 500 K, σ500 = 0.13 S/cm). In tysonite-structured crystals, the highest ionic conductivity was found for LaF 3: 3 mol % SrF2 (σ500 = 2.4 × 10−2 S/cm). Different types of coordination polyhedrons and their different linking in orthorhombic and tysonite structures explain a large difference between conductivities in both structures. Published in Russian in Elektrokhimiya, 2009, Vol. 45, No. 6, pp. 668–678. The article is published in the original. Published by report at IX Conference “Fundamental Problems of Solid State Ionics”, Chernogolovka, 2008. |
