Synthesis and characterization of niobium doped hexagonal tungsten bronze in the systems, CsxNbyW1−yO3

Samples of nominal compositions, Cs0.25Nb y W1−y O3 and Cs0.3Nb y W1−y O3 with 0.0 ≤ y ≤ 0.25 and 0.0 ≤ y ≤ 0.3 were synthesized using appropriate amounts of Cs2WO4, WO3 and WO2 in evacuated and closed silica glass tubes at 800 °C. The polycrystalline products contain hexagonal shaped crystals of up to 15 μm diameter as long as y ≤ 0.15. X-ray powder patterns of the samples reveal the formation of hexagonal tungsten bronze (HTB-I) type phase with y 0.1 and the effect of counterdoping by Nb5+/W5+ substitution in the metallic HTB-I type phase for y ≤ 0.1, respectively. Reinvestigations in the system Rb0.3Nb y W1−y O3 (0.0 ≤ y ≤ 0.175) show similar results with increasing content of HTB-II type phase related with y.