HIGH-PRESSURE PHASES IN THE SYSTEM W-O .1. STRUCTURE OF WO1.09 BY HRTEM

A new type of tungsten oxide was synthesized from a mixture of W and WO3 by a solid-phase sintering method under high-pressure conditions. The crystal structure of the new oxide WO1.09 was investigated by selected-area electron diffraction and high-resolution transmission electron microscopy (HRTEM). It has the following unit-cell parameters: a = 17.16, b = 10.32. c = 3.78 angstrom, V = 669 angstrom3, Z = 44, rho = 21 (3) g cm-3, and belongs to the space group Cmm2. The W positions were determined from computer-processed HRTEM structure images. The R-factor minimization procedure was used to refine cationic sites; R' = 14.5%. It is shown that the crystal structure is formed by edge sharing WO3 octahedrally and tetrahedrally coordinated W cations.