Structural, magnetic and optical behavior of pristine and Yb doped CoWO4 nanostructure

Nanocrystalline pure and Yb doped CoWO4 nanostructures were synthesized successfully by single step chemical precipitation technique. The prepared sample was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and thermal analysis (TGA). XRD pattern reveals the pure and doped CoWO4 nanoparticles belongs to the monoclinic structure with the space group of P-2/c. Electron microscopy studies clearly evidence the formation of round edged nanocubes with an average particle size of 60-80 nm, emerges in the polycrystalline nature. UV-Visible absorption spectra of Yb3+ doped CoWO4 nanocrystals shows a strong absorption peak at 278 nm due to CoWO4 metal to ligand charge transfer within the [WO6](6-) complex. Photoluminescence spectra of pure and doped CoWO4 nanostructures substantiate the effect of Yb on the wolframite structure and its response for optical behavior. These results suggest that the addition of Yb into the Co-site on CoWO4 has no significant contribution for luminescent enhancement when compared to pure one up to 5 % Yb concentration. Typical magnetization curve shows the mixed ferromagnetic and diamagnetic transition of CoWO4 with respect to the Yb doping concentration.