Phase Relations in the Al2O3-V2O5-MoO3 System in the Solid State. The Crystal Structure of AlVO4

Phase relations in the ternary oxide system Al2O3-V2O5-MoO3 in the solid state in air have been investigated by using the x-ray diffraction (XRD) and differential thermal analysis/thermogravimetric (DTA/TG) methods. It was confirmed that in the subsolidus area of the Al2O3-V2O5-MoO3 system, there exist seven phases, that is Al2O3, V2O5(s.s.), MoO3, AlVO4, Al-2(MoO4)(3), AlVMoO7, and V9Mo6O40. Seven fields, in which particular phases coexist at equilibrium, were isolated. The crystal structure of AlVO4 has been refined from x-ray powder diffraction data. Its space group is triclinic, P (1) over bar, Z = 6, with a = 0.65323(1) nm, b = 0.77498(2) nm, c = 0.91233(3) nm, alpha = 96.175(2)degrees, beta = 107.234(3)degrees, gamma = 101.404(3)degrees, V = 0.42555 nm(3). The crystal structure of the compound is isotypic with FeVO4. Infrared (IR) spectra of AlVO4 and FeVO4 are compared.