Synthesis and crystal structure of sodium–bismuth polyphosphate NaBi(PO 3) 4

Abstract

Synthesis and complete structural characterization by X-ray diffraction and IR are given for sodium–bismuth polyphosphate NaBi(PO 3) 4. This compound is monoclinic P2 1/n with a structural type II and with the following unit-cell dimensions: a = 0.7194 ( 1 ) nm , b = 1.3097 ( 2 ) nm , c = 0.9858 ( 2 ) nm , β = 90.43 ( 1 ) ° , V = 0.9288 ( 3 ) nm 3 , Z = 4 and d cal = 3.918 . The structure was solved from 3097 independent reflections with R 1 = 0.0211 and WR 2 = 0.0527 , refined with 164 parameters. The atomic arrangement can be described as a long chain polyphosphate organization, helical ribbons (PO 3) n . The ribbons run along the shortest unit-cell directions with a period of four tetrahedra. Bismuth atoms have an eight-fold coordination while sodium atoms have seven oxygen neighbours. IR spectra at room temperature, was investigated in the frequency range 400–1500 cm –1, show clearly some characteristic bands of infinite chain structures of PO 4 tetrahedra linked by a bridge oxygen.