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

Resumo

The phases NdF₃ (I), x (II), NdTi₂O_4.75F_0.5(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 H₆NdF_7.8(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.