Synthesis and structural characterization of AMV(2)O(8) (A = K, Rb, Tl, Cs; M = Nb, Ta) vanadates: a structural comparison of A(+)M(5+)V(2)O(8) vanadates and A(+)M(5+)P(2)O(8) phosphates

摘要

Eight new quaternary vanadates of niobium and tantalum, AMV(2)O(8) (A = K, Rb, Tl, Cs; M = Nb, Ta), have been prepared by solid state reactions and structurally characterized by single crystal and powder X-ray diffraction (XRD) techniques. The two cesium compounds, unlike the known CsSbV2O8 with a layered yavapaiite structure, have a new three-dimensional structure and the other six compounds possess the known KSbV2O8 structure type. The three types of [(MV2O8)(-)](infinity) anionic frameworks of twelve A(+)M(5+)V(2)O(8) (A = K, Rb, Tl, Cs; M = Nb, Ta, Sb) vanadates could be conceived to be built by different connectivity patterns of M2V4O18 ribbons, which contain MO6 octahedra and VO4 tetrahedra. A structural comparison of these twelve vanadates and the nineteen A(+)M(5+)P(2)O(8) phosphates has been made. The spectroscopic studies of these eight new quaternary vanadates are presented.