Synthesis of CaF$_2$–YF$_3$ nanopowders by co-precipitation from aqueos solutions

Study of the CaF$_2$–YF$_3$ system by co-precipitation from aqueous nitrate solutions revealed the formation of Ca$_{1-x}$Y$_x$F$_{2+x}$ solid solution precipitate containing up to 20 mol. % yttrium fluoride (x $\le$ 0.2). A higher yttrium to calcium ratio in the starting solutions caused additional precipitation of orthorhombic $\beta$-YF$_3$ nanophase elongated along the $\langle b\rangle$ axis. Cubic (H$_3$O)Y$_3$F$_{10}$ phase was also formed (SSG $Fm3m$, $\alpha$=11.60 $\mathring{\mathrm{A}}$, KY$_3$F$_{10}$ structural type).