Tapas Debnath

New series of vanadium-doped hexagonal tungsten bronze, MxW1−yVyO3

Attempts were taken to synthesize vanadium doped rubidium and cesium hexagonal tungsten bronze samples with nominal composition MxW1-yVyO3 (x =0.30, 0.25 and 0.0 ≤ y ≤ x). The samples were synthesized by solid state synthesis method at 700 ̊C in an evacuated silica glass tube. X-ray diffraction data of MxW1-yVyO3 reveal that pure hexagonal tungsten bronze (HTB) phase could be formed up to y = 0.18 and y = 0.15 for x = 0.30 and x = 0.25 series, respectively revealing 60% of replacement of W5+ by V5+. Rietveld structure refinement of XRD data also reveal the systematic incorporation of vanadium in the HTB lattice and shortening of the V/W-O bond distances within the xy plane and elongation in the crystallographic c direction. FTIR absorption spectra of the oxidized phases also support the XRD results. Moreover, there develop an absorption feature as a function of y and shows a significant increase of its intensity with gradual replacement of W5+ by V5+, indicating a significant decrease in the metallic like contribution and reveals nonmetallic nature of the compounds. Elemental analysis show excellent agreement with their nominal ones indicating that a systematic incorporation of vanadium in MxW1-yVyO3 system. -----#Present address of Altaf Hussain: Bangabandhu Sheikh Mujibur Rahman Maritime University, Bangladesh.

Synthesis and characterization of vanadium-doped alkali metal tungsten bronzoid

Attempts were made to prepare a series of vanadium doped alkali metal hexagonal tungsten bronzoid1, AxVxW1-xO3 (A= K; Cs and x = 0.15-0.30), at comparatively low temperature by organic precursor method. The prepared samples were characterized by X-ray powder Diffraction, Fourier Transform Infrared spectroscopy, Energy-dispersive X-ray analysis and Scanning Electron Microscopy. XRD data of AxVxW1-xO3 reveals that pure hexagonal tungsten bronzoid phase could be formed at 400oC by this method. However, a second unknown phase along with the hexagonal bronzoid phase appeared with x= 0.30 composition when annealed at higher temperature.