OPTICAL ABSORPTION SPECTRA OF SAMARIUM DOPED TeO2-Na2O GLASSES

Abstract

In this paper the modification of optical absorption spectra characteristics of tellurite glasses doped by Sm3+ ions has been studied. Sodium-tellurite glasses have a composition (80-x) TeO2-20Na2O-xSm2O3 with concentration (x=0, 0.3, 0.6, 1, 1.2, 1.5) were synthesized by melt-quenching technique. Physical and optical parameters are calculated from absorption spectra and by measuring the density of the samples. The maximum density is found to be (5.019 g cm-3) for 1.2 mol% of Sm3+ ions. The variations in the polarizability (4.758-4.863 cm3) and the molar volume (28.359–28.919 cm3mol-1) with dopant concentration are ascribed to the formation of non-bridging oxygen. This observation is consistent with the alteration of number of bonds per unit volume. The amorphous nature of the prepared glasses were confirmed by using x-ray diffraction (XRD) pattern. The UV spectra of the prepared sample have been measured at room temperature and at a wavelength range 200-1000 nm. The recorded absorption spectra exhibit nine absorption picks represented by transition bands 6H5/2→6P3/2, 4I11/2, 6F11/2, 6F9/2, 6F7/2, 6F5/2, 6F3/2, 6H15/2 and 6F1/2. The values of the optical band gap are found to lie between 3.044 eV -3.186 eV, while Urbach energy (Eu) values varies between 0.312 eV -0.209 eV. The optical energy gap for indirect forbidden transition has increased whereas the values of Urbach energy have decreased with the increasing of Sm2O3 content. The absorption cut-off wavelength (λc) in the range 360.8nm 366.15nm calculated from the UV spectra and it depend on the Sm3+ concentration, the optical properties were found to be strongly affected by the varying concentration of Sm3+ ions.