Effect of Bismuth on Physical and Spectroscopic Properties of ZnO-Li2B4O7-TbF3 Glasses

The effect of Bismuth on zinc-lithium tetra borate glasses were discussed based on structural, physical, and spectroscopic properties. Glass systems of Bi2O3-ZnO-Li2B4O7-TbF3 [BZLT] were cast by melt-quench process. Transparent glasses were analysed by diffracted Roentgen X-rays. Peak free and broad nature X-ray diffraction revealed the amorphous arrangement prevailing in these glasses. Density was estimated using the Archimedes principle. Bismuth grossly affected the density of BZLT glasses by increasing its value 2.722 gm/cc [BZLT-0] to 4.6739 gm/cc [BZLT-40]. Optical absorption provides valuable information about optical band gap energy and Urbach energy and some of its derived physical quantities. The effect of bismuth is felt in decreased Eopt values [3.312 eV in BZLT-0] [2.619 eV in BZLT-40] in BZLT glasses. Bismuth altered the structure of the borate network by forming non-bridging oxygens which in turn reduced the band gap energy by large margin (ΔEopt = 0.693 eV). Fourier transform infrared spectroscpy and Raman studies revealed the presence of several triangular BO3 and tetrahedral BO4 and BiO3 units and also the existence of metal cation vibrations and supported the large deviations in the optical bandgap energies. Election paramagnetic resonance studies support the presence of Tb3+ ions and absence of Tb4+ions in BZLT glasses.