Optical band gap and Raman spectra in some (Bi2O3)x(WO3)y(TeO2)100-x-y and (PbO)x(WO3)y(TeO2)100-x-y glasses

The glasses representing (Bi2O3)(x)(WO3)(y)(TeO2)(100-x-y) and (PbO)(x)(WO3)(y)(TeO2)(100-x-y) systems were prepared. The dilatometric glass-transition temperatures of examined glass samples were found in the region 383-434 degrees C, the coefficient of thermal expansion varied from 12 to 16 ppm/degrees C and the density ranged from 6.30(2) to 6.80(8) g/cm(3). From the optical transmission measurements of thin glassy bulk samples prepared by a glass blowing, the optical gap values were found in the narrow region 3.21-3.36 eV. For the temperature interval 300-480 K, the values of the temperature coefficient of the optical band gap varied from 3.7 x 10(-4) to 5.24 x 10(-4) eV/K. It is suggested that Raman feature observed at around 350 cm(-1) can be assigned to an overlap of Raman bands attributed to WO6 corner shared octahedra and to the following three atomic linkages: Bi-O-Te, Pb-O-Te and W-O-Te. (C) 2009 Elsevier B.V. All rights reserved.