A monophosphate molybdenum bronze built up from ReO3-Type slabs: Ag0.7Mo3O7(PO4)

摘要

A monophosphate molybdenum bronze Ag-2.8(PO2)(4)(MoO3)(12) has been synthesized for the first time. This monoclinic bronze (a=23.857(3)Angstrom, b=5.2990(6)Angstrom, c = 6.5659(4)Angstrom, beta = 93.950(6)degrees) represents the m=6 member of the A(x)(PO2)(4) (MO3)(2m) family (M = W, Mo). Its structure, which consists of ReO3-type slabs interconnected with monophosphate groups, is very similar to those of the m = 6 members K-x(PO2)(4)(WO3)(12) and Mo4O11, forming hexagonal tunnels where the Ag+ cations are located. The distribtion of Ag+ in the tunnels is however different from that of K+ in the phosphate tungsten bronze: two sites are partially occupied close to the walls of the tunnels so that Ag+ exhibits a ninefold and a tetrahedral coordination. The resistivity measurements, although performed on polyphasic samples, clearly show a semiconducting behavior. The possibility of charge density wave properties is considered. (C) 1998 Academic Press. [References: 18]