Phase Formation in the TiO2–H2SO4–HF–Nd(NO3)3–H2O System at 20°C

Abstract

The phases NdF3 (I), x (II), NdTi2O4.75F0.5(SO4)0.5 · 3H2O (III), NdTiF3(SO4)2 · 6H2O (NdTiOF(SO4)2 · 6H2O) (IV), Nd2(SO4)3 · 8H2O (V), and Nd2(SO4)3 · 4H2O (VI) formed in sulfuric acid and fluorine-containing solutions during the synthesis of materials from feedstocks and the purification and separation of metals were separated. The regions of their existence were schematically presented. Particles with a “core-shell” structure were detected. The compounds were studied by elemental, crystallooptic, X-ray diffraction, and thermal analyses. The composition was determined for phase III (from thermogravimetric (TG) data) and spherolith-like particles of H6NdF7.8(SO4)0.5 · 3.75H2O (VII) (by X-ray diffraction microanalysis). Freshly separated particles evolved HF. Phase IV corresponding to NdTiF3(SO4)2 · 6H2O (according to TG data) acquired the composition and form of the known NdTiOF(SO4)2 · 6H2O phase after storage.