SUBSTITUTION OF TUNGSTEN BY TANTALUM IN TUNGSTEN BRONZES, NAXTAYW1-YO3

In order to study the modification of the transport properties of NaxWO3 by substitution in the WO3 sublattice, single crystals of tantalum-substituted tungsten bronzes of formula NaxTayW1-yO3 have been grown by electrolytic reduction of fused Na2WO4WO3Ta2O5 mixtures. The lattice constant of their cubic perovskite like structure increases with Ta content. Electric conductivity measurements on NaxTayW1-yO3 single crystals characterize a metal-non metal transition when x-y, i.e. the number of d electrons, decreases. This transition seems to be of Anderson type. © 1979.