Synthesis and thermal behaviour of pauflerite, β-VOSO4, and its α-modification

Abstract

Abstract Powder α-VOSO4 was prepared by dehydration of VOSO4·3H2O. β-VOSO4 was synthesized by boiling of V2O5 in H2SO4. Thermal behaviour of VOSO4·3H2O, α- and β-VOSO4 modifications is studied by high-temperature powder X-ray diffraction and thermal analysis, including two-step dehydration of VOSO4·3H2O, formation of α-VOSO4, thermal expansion and decomposition of both modifications into V2O5. Higher anisotropy of thermal expansion of the tetragonal α-modification α c = 39(2)·10–6 K–1 along the vanadyl ion and α a = 2.4(6)·10–6 K–1 in the perpendicular direction) comparing to the orthorhombic β-modification (α a = 20.2(7), α b = 2.8(8), α c = 17.8(4)·10–6 K–1) is explained from a crystal chemical point of view.