Synthesis and characterization of niobium doped hexagonal tungsten bronze in the systems, Cs(x)Nb(y)W(1-y)O(3)

• Samples of nominal compositions, Cs(0.25)Nb (y) W(1-y) O(3) and Cs(0.3)Nb (y) W(1-y) O(3) with 0.0 a parts per thousand currency sign y a parts per thousand currency sign 0.25 and 0.0 a parts per thousand currency sign y a parts per thousand currency sign 0.3 were synthesized using appropriate amounts of Cs(2)WO(4), WO(3) and WO(2) in evacuated and closed silica glass tubes at 800 A degrees C. The polycrystalline products contain hexagonal shaped crystals of up to 15 mu m diameter as long as y a parts per thousand currency sign 0.15. X-ray powder patterns of the samples reveal the formation of hexagonal tungsten bronze (HTB-I) type phase with y < 0.1. A mixture of HTB-I and an analogous less reduced hexagonal tungsten bronze (HTB-II) type phase is seen when y a parts per thousand yen 0.1. HTB-II content increases with increasing y, revealing close similarity to bronzoid type phases when y = x. Results of SEM/EDX analysis also support a partial substitution of tungsten by niobium in the HTB-I type phase. Infrared absorption and optical reflectivity data shows the effect of increasing amount of non-metallic phase for y > 0.1 and the effect of counterdoping by Nb(5+)/W(5+) substitution in the metallic HTB-I type phase for y a parts per thousand currency sign 0.1, respectively. Reinvestigations in the system Rb(0.3)Nb (y) W(1-y) O(3) (0.0 a parts per thousand currency sign y a parts per thousand currency sign 0.175) show similar results with increasing content of HTB-II type phase related with y.

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NATURVETENSKAP  -- Kemi -- Materialkemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Materials Chemistry (hsv//eng)

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