Spectroscopic investigations of nanosized Cr 3+ doped Sc 2-x In x (WO 4 ) 3 : A new promising laser material.

Chromium(III) doped nanosized Sc2-x Inx (WO4 )3 , (x = 0-2) solid solutions were prepared by the co-precipitation/calcination method. The obtained powders were characterized using X-ray diffraction (XRD), electron paramagnetic resonance (EPR), infrared (IR), absorption and luminescence spectra. X-ray analysis showed that the compounds are pure solid solutions with orthorhombic symmetry at x values 0 and 0.5 and with monoclinic symmetry for x values 1.0, 1.5 and 2.0. The calculated crystallite size ranged from about 20 to 110 nm, except for Sc2 (WO4 )3 characterized by considerably larger sizes. IR spectra of the solid solutions contain the characteristic vibrations of the WO4 and MeO6 , (Me = Sc, In) polyhedra, building the Sc2 (WO4 )3 and In2 (WO4 )3 structures. EPR analysis proved the presence of isolated Cr3+ ions in the crystal field with rhombic symmetry. The presence of Cr3+ in sites with weak and strong crystal field was revealed by absorption and luminescence spectra. This study demonstrates the effect of hosts crystal symmetry, particles size and doping concentration on the luminescence properties.