Solid-state properties of some polycrystalline alkali-metal tungsten bronzes

Abstract

The structures, electrical conductivities, oxygen deficiencies and surface activities of polycrystalline Li, Na and K bronzes of tungsten with varying alkali-metal contents have been considered in detail for the first time. There is clear evidence that as the temperature is raised so ionic mobility makes a significant contribution to the total electrical conduc­tivity. The processes involved in ionic mobility may be diffusion of O 2− lattice anions, the intercalate alkali-metal ion M + , and a lower oxidation-state lattice cation W y + ( y < 6). All bronzes studied are shown to be oxygen deficient (to an extent that increases with the concentration of the alkali-metal intercalate) and, because their ionic conductivity is similar to that of lower oxides, O 2− migration may be more significant than previously recognized.