Fluorination of Eu-doped layered yttrium hydroxides: the role of anionic composition

The fluorination processes of layered rare-earth hydroxides (LRHs) intercalated with various anions, including organic ones, have been compared for the first time. The fluorination process was investigated for chloride-, nitrate- and 4-sulfobenzoate-intercalated Eu-doped layered yttrium hydroxides by interaction with aqueous solutions of sodium fluoride at 100–150$^\circ$C for 2–48 hours. The final product of fluorination in all cases is the hexagonal yttrium hydroxide fluoride (YHF) phase of Na$_y$Y$_{0.95}$Eu$_{0.05}$(OH)$_{3+y-x}$F$_x$ $\cdot$ $m$H$_2$O ($x\sim$ 3, $y\sim$ 0.2) composition. The formation rate of the YHF increases with the interlayer spacing of the Eu-doped layered yttrium hydroxide.