Abstract

SYNTHESIS, STRUCTURAL, OPTICAL AND THERMAL PROPERTIES OF PURE AND GD3+ DOPED MNWO4 COMPOUNDS

P. Prabukanthan*, R. Aswini and S. Niresh Babu

Abstract

Pure and Gd3+ doped manganese tungstate (MnWO4) compounds semiconductors were prepared by solid-state metathetic approach assisted microwave irradiation using sodium tungstate (Na2WO4·2H2O), Gd(CH3COO)3 and MnCl2 solutions as precursors. The morphology and crystal phase of the as-synthesised pure and Gd3+ doped manganese tungstate were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The above characterizations render that the products obtained belong to the wolframite-like monoclinic crystal system, with average size of cuboid nanoparticles about 150 nm to 300 nm in the pure Gd3+ doped MnWO4. In the diffuse reflectance UV-Visible absorption spectra shows that the strong absorption maximum of ~359 nm was observed for pure and Gd3+ doped MnWO4. Due to the high crystallinity the samples have shown more prominent UV absorption maxima. The strong band located at about 359 nm can be assigned to the intense band to band transition corresponding to the absorption between the O 2p level and Mn 3d level. The weak band located at about 903 nm can be assigned to spin-forbidden transitions of an electron from eg orbital to t2g orbital of Mn2+ (3d5) ions. Photoluminescence (PL) spectra shows that the three characteristic emission band at around 415 nm, 487 nm and 505 nm for pure MnWO4 ascribes the intrinsic optical behaviour of the host system. The oxidation state of manganese (Mn) and gadolinium (Gd) were investigated using electron paramagnetic resonance (EPR) spectroscopy.

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