The solubility of sodium and potassium fluorides in strontium fluoride

The phase diagram of the NaF-SrF$_2$ system was studied by thermal analysis and X-ray powder diffraction analysis with the determination of the chemical composition. The system was found to be of the eutectic type. The eutectic coordinates are 853$^\circ$C, 32 mol % SrF$_2$. A narrow range of the existence of solid solution Sr$_{1-x}$Na$_x$F$_{2-x}$ was established. The NaF solubility reaches a maximal value of $x$ = 0.035 at eutectic temperature. The solubility of KF in SrF$_2$ is very low.