Role of aluminum on the physical and spectroscopic properties of chromium-doped strontium alumino borate glasses

The glass samples were prepared in accordance with the formula: (30 - x)SrO-xAl(2)O(3)-69.8B(2)O(3)-0.2Cr(2)O(3) (0 <= x <= 15 mol%) by melt quenching method. The absence of Bragg's peaks confirmed the amorphous nature of the prepared glass samples. It was observed that the molar volume was increasing while the density is decreasing with increasing of Al2O3 content. Optical absorption study was performed to evaluate the optical bandgap, oxygen packing density, ionic packing density and Urbach energies. The Racah parameters (B and C) and D-q/B ratio have been calculated. Fourier transform infrared (FTIR) spectra recorded in the region from 400-1600 cm(-1) at room-temperature (RT) confirmed the formation of BO3, BO4 and AlO4 groups upon the addition of strontium oxide as modifier. The Raman spectra of all the glasses recorded over continuous spectral range 200-1600 cm(-1) exhibited different spectral bands. The EPR spectra recorded at 9.7 GHz (X-band frequency) have four resonance signals. The signal at g approximate to 5.33 is due to Cr3+ ion sites of rhombic symmetry and signal at g approximate to 1.97 is due to contribution from Cr3+ and Cr5+ ion pairs.