Crystal structure and properties of the new vanadyl(IV)phosphates Na2MVO(PO4)2, M=Ca and Sr

V. V. CHERNAYA; A. A. TSIRLIN; R. V. SHPANCHENKO; E. V. ANTIPOV; A. A. GIPPIUS; E. N. MOROZOVA; V. DYAKOV; J. HADERMANN; E. E. KAUL; C. GEIBEL

JOURNAL OF SOLID STATE CHEMISTRY

Elsevier

Año: 2004 vol. 177 p. 2875 - 2880

0022-4596

Two new complex vanadyl(IV)phosphates Na2MVO(PO4)2 (M=Ca, Sr) were synthesized in evacuated quartz ampoules and investigated by means of X-ray diffraction, electron microscopy, DTA, ESR and magnetic susceptibility measurements. The crystal structure of Na2SrVO(PO4)2 was solved ab-initio from X-ray powder diffraction data. Both compounds are isostructural: a = 10.5233(3)Å , b = 6.5578(2) Å , c = 10.0536(3) Å and a = 10.6476(3) Å , b = 6.6224(2) Å , c = 10.2537(3) Å for Ca and Sr, respectively; S.G. Pnma, Z = 4. The compounds have a three-dimensional structure consisting of V4+O6  octahedra connected by PO4 tetrahedra via five of the six vertexes forming a framework with cross-like channels. The strontium and sodium atoms are located in the channels in an ordered manner. Electron diffraction as well as high-resolution electron microscopy confirmed the structure solution. The new vanadylphosphates are Curie–Weiss paramagnets in a wide temperature range down to 2K with q = 12 and 5K for Ca and Sr phases, respectively.