Department of Chemistry, University of Dhaka
○Subrata Chandra Roy Altaf Hussain

Tungsten bronzes,M_xWO_3, are well known non-stoichiometric ternary metal oxides where M is typically an electropositive metal and 0<x<1. Among tungsten bronzes, the alkali metal tungsten bronzes are extensively studied compounds. Fully oxidized, isostructural phases termed as bronzoids_, M_xNb_yW_1-yO₃, and partially oxidized bronzes of alkali metals have also been reported.

In our present investigation, powder samples of potassium tetragonal tungsten bronzes (TTB), K_xWO₃ , and niobium substituted TTB, K_xNb_yW_1-yO₃, were prepared by the conventional solid-state method at 800^oC. The powder samples were characterized by X-ray powder diffraction technique.

XRD patterns of K_0.50WO₃ and K_0.55WO₃ show TTB phase while the sample with composition K_0.45WO₃ shows a mixture of TTB and hexagonal tungsten bronzes (HTB) phases.

Attempts to substitute Nb in K_0.45WO₃ result mixtures of HTB and TTB phases and with y > 0.1 the TTB phase disappears giving rise to an orthorhombic phase along with HTB. While for the systems K_0.50Nb_yW_1-yO₃ and K_0.55Nb_yW_1-yO₃ a single phase of TTB is observed upto y = 0.05 and y = 0.07 respectively. Further substitution of Nb in these compositions results mixture of TTB and HTB phases.