Growth and Some Physical Properties of Congruently Melting Fluorite Solid Solutions Crystals in the CaF2–SrF2–RF3 (R = La, Ce) Systems

Abstract

Congruently melting Ca_0.77Sr_0.07La_0.16F_2.16 and Ca_0.70Sr_0.11Ce_0.19F_2.19 fluorite solid solutions crystals in the CaF₂–SrF₂–RF₃ (R = La, Ce) systems have been grown from melt by the Bridgman technique in a fluorinating atmosphere. Their optical, mechanical, electrophysical, and thermophysical characteristics have been studied. The crystals are transparent in a wide spectral range; their refractive indices are n_D = 1.468 (R = La) and 1.479 (R = Ce), and their microhardness (Н_V ∼ 5.0 GPa) and ionic conductivity (σ ∼ 3 × 10^–3 S/cm at 823 K) exceed significantly the corresponding values for CaF₂ and SrF₂ crystals. The materials under study are promising isomorphic-capacious crystalline matrices for various applications in photonics and solid-state ionics.