CaSrF2

CaSrF2, or calcium strontium fluoride, is a binary fluoride that represents a complete solid solution between calcium fluoride (CaF2) and strontium fluoride (SrF2). The composition is often expressed as Ca1−xSrxF2 with 0 ≤ x ≤ 1, reflecting the continuous range of Ca–Sr mixtures. In most compositions, CaSrF2 adopts the fluorite-type crystal structure, the same structure shared by CaF2 and SrF2. This means a cubic lattice where fluoride ions form a face-centered cubic array and the divalent cations (Ca2+ and Sr2+) occupy the cation sublattice, mixing on the lattice sites according to composition.

Synthesis of CaSrF2 generally involves solid-state reaction or high-temperature mixing of CaF2 and SrF2 precursors, followed by controlled crystallization to obtain bulk crystals or polycrystalline powder. The material is typically prepared under conditions that minimize moisture sensitivity and fluoride volatility, and single crystals or high-purity powders can be grown for optical applications.

Properties of CaSrF2 are dominated by its fluorite-related lattice. It is chemically robust, with wide transparency common to alkaline earth fluorides, extending across portions of the ultraviolet to near-infrared depending on quality and dopants. The lattice parameter varies with composition in a manner approximated by Vegard’s law, enabling tuning of optical properties such as refractive index and lattice spacing through the Ca/Sr ratio. Like other CaF2-family hosts, CaSrF2 is studied as a potential host lattice for dopants in lasers and nonlinear optical devices.

See also: calcium fluoride, strontium fluoride, fluorite structure.