Crystal structure and magnetic properties of orthorhombic Sr2VO4 with tetrahedral vanadium(IV)

A new crystalline modification of Sr2VO4, isostructural with Sr2CrO4, has been prepared by both low and high temperature methods. The space group appears to be Pna21 with a = 14.092(4) Å, b = 5.806(2) Å, and c = 10.106(3) Å. Atomic positions have been refined by the Rietveld method from powder neutron and X-ray diffraction data. The structure is a supercell of the K2SO4-type and thus appears to be the first example of an oxide containing VO−44 polyhedra. This phase is apparently a high temperature modification stable above about 1100°C. Orthorhombic Sr2VO4 can also be prepared at low temperature (about 500°C) by reduction of Sr2VO4Cl with Na metal. Surprisingly, the magnetic susceptibility shows a broad maximum at 60 K and the data can be understood very well on a S = 12 dimer model. These results are compared with similar ones for electronically related Cu(II) salts.