Synthesis and crystal structure of a novel lithium bismuth phosphate, Li2Bi14.67(PO4)6O14

A lithium bismuth phosphate, $Li_2Bi_{14.67}(PO_4)_6O_{14}$, has been synthesized for the first time by the solid-state method. The crystal structure was determined by single crystal X-ray diffraction at 150 K. $Li_2Bi_{14.67}(PO_4)_6O_{14}$ crystallizes in the monoclinic system C2/c (No.15), with a = 30.8189(4) angstrom, b = 5.2691(3) angstrom, c = 24.5302(3) angstrom, \beta = 122.84(2)degrees, V = 3346.81 (1) angstrom(3) and Z = 2. The structure along the b axis consists of layers of [Bi2O2] units as the basic building block. These are separated by isolated $PO_4$ and $LiO_4$ tetrahedra. The oxygen co-ordination around two of the phosphorus atoms is disordered. Solid-state $^7Li$ NMR studies confirm the presence of lithium in the structure. The material shows ionic conductivity of the order of $10^{-5} S cm^{-1}$ at 600 $^oC$.