Glycothermal reaction of various vanadium compounds with triethyl phosphate yielded two hydrate phases of vanadium(III) phosphate having tetragonal (Phase 1) and monoclinic (Phase 2) crystal systems, depending on the reaction conditions such as phosphorus/vanadium ratio, vanadium starting material, reaction temperature and solvent. Thermal treatment of Phase 2 in an anaerobic condition caused transformation to Phase 1 which finally transformed to VPO4 through an intermediate phase (Phase M). Heat treatment of both the phases in an aerobic condition caused the formation of beta-VOPO4. (c) 2006 Springer Science + Business Media, Inc.