Abstract
The concentration series of nonstoichiometric crystals Ca1–xYxF2+x (x = 0.01–0.14) was obtained from a melt by directional crystallization to refine the composition of the temperature maximum on the melting curves. A precision (±9 × 10−5 Å) determination of lattice parameters of the Ca1–xYxF2+x crystals with the structure of fluorite (sp. gr. Fm-3m) was performed, and a linear equation of their concentration dependence was calculated: a(x) = 5.46385(5) + 0.1999(4) x. The distribution of yttrium along the crystals Ca1–xYxF2+x, the content of which is determined by the precision lattice parameters, is studied. The congruently melting composition x = 0.105(5) of the Ca1–xYxF2+x phase is refined by the method of directional crystallization.
Highlights
This work is dedicated to the anniversary of this discovery, which was followed by the epoch-making development of nonstoichiometry in inorganic fluorides of alkaline earth and rare earth elements and fluoride materials science
The scientific basis for the search for new multicomponent fluoride materials was the study of phase diagrams of more than 200 systems of the MFm –RFn (M, R −27 metals; m, n ≤ 4) in order to search for new phases
The aim of the work is to obtain single crystals of Ca1–x Yx F2+x (x = 0–0.14) by directional crystallization of a melt and to determine the concentration dependence of the precision lattice parameters to clarify the composition of the phase with a congruent melting
Summary
The need for new materials that are transparent in the short-wavelength range of a spectrum can be met by obtaining crystals of complex composition with improved properties. Such materials include crystals of strongly nonstoichiometric phases with the structure of fluorite - Ca1–x Yx F2+x (x < 0.38) solid solutions. Despite the prospects of M1–x Rx F2+x crystals as an alternative, if necessary, to singlecomponent MF2 fluorides, the latter have been and remain the only optical structural materials for the VUV, UV, and mid-IR spectral ranges. The prospects of some crystals of multicomponent nonstoichiometric fluorides as optical materials for the VUV spectral range were considered in [3]. Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
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