Phase equilibria in BaF <sub>2</sub> - SmSF section of BaF <sub>2</sub>-SmF <sub>3</sub>-Sm <sub>2</sub>S <sub>3</sub>-BaS quadrangle
X-ray and microstructural analyses of the samples of the BaF <sub>2</sub> - SmSF section located in the irregular BaF <sub>2</sub>-SmF <sub>3</sub>-Sm <sub>2</sub>S <sub>3</sub>-BaS quadrangle are carried out. When SmSF content changes, the phase composition of samples in the section also changes. Six areas are identified in the section according to the phase composition of samples. The phases of nonstoichiometric composition are formed in BaF <sub>2</sub> - SmSF section based on barium fluoride: Ba <sub>1-x</sub>Sm <sub>x</sub>F <sub>2+x</sub> of 25 mol. % SmSF is replaced by the phase of Ba <sub>4±х</sub>Sm <sub>3±x</sub>F <sub>17±x</sub> composition. The increase in the concentration of samarium ions results in the monotonic decrease of the cube cell parameters of nonstoichiometric phases. It is discovered that a phase of unknown composition is formed in the samples of BaF <sub>2</sub> - SmSF from 25 to 55 mol. % SmSF section of 25-55 mol. % SmSF. It is supposed that there are cations and anions of two types in the compound and on the basis of this compound the solid solution area is formed. The further study of BaF <sub>2</sub>-SmF <sub>3</sub>-Sm <sub>2</sub>S <sub>3</sub>-BaS quadrangle is required to determine the composition and structure of the compounds formed. BaSm <sub>2</sub>S <sub>2</sub>F <sub>4</sub> compound is not formed in this section. In BaF <sub>2</sub> - SmSF section,