Juliet Josephine Joy. J

ABSTRACT

Wolframite type pure andNd-doped CoWO4 were synthesized by easy and effective chemical precipitation technique. Typical monoclinic phase and crystal structure of the samples were confirmed from the XRD pattern. Well defined nanocubicalmorphology with round edges of the pure and doped samples were confirmed from the electron microscopy analysis. UV-Vis spectra for pure and Nd3+ doped CoWO4 demonstrates that the excellent optical behaviour of the wolframite cobalt tungstates nanostructure. Optical energy band gap was varied with the doping as well as calcination temperature ascribes to the changes in the electronic structure. From the band gap calculation it is confirmed that the observed band gap is direct which is not belongs to the indirect. Further, the red shift in the absorption edge substantiates the formation of nanacrystalline CoWO4 and thus evidences the incorporation of Nd into Co lattice site completely. The strong PL emission peak was centered at 455 nm region for all the samples due to the radtiative transition within the [WO4]-4 tetrahedral group. The relative intensity of the emission band reduced and at 5 mole% doping it is almost no emission was observed. This luminescent quenching is confirms the lower annihitaion process in doped CoWO4 nanostructure when compared to pure wolframite. Overall, from this study tuning of an electronic structure by doping will influences on the optical band gap as well as PL emission in the CoWO4 nanostructure. Keywords : Chemical synthesis, Wolframite, optical band gap, luminescent quenching.