Comparative studies of structural and optical properties of Nb2O5–Sb2O3–TeO2 glass and glass-ceramics

A new, transparent antimony-tellurite glass and glass-ceramic systems doped with Nb2O5 have been prepared by using the conventional melt quenching method and heat treatment process, respectively. Various physical, optical and structural studies were reported through XRD, TEM, SEM, ultraviolet-visible, Raman, infrared and ESR investigations. XRD analysis of glass and glass-ceramic samples revealed their amorphous and crystalline natures, respectively. The Williamson-Hall approach was used to determine the average crystallite size of synthesised glass-ceramics and the values were found to be in the range of 23 to 85 nm. The SEM result reveals that glass-ceramics contain perspicuous and haphazardly distributed nanoclusters possessing sizes in the range of 45 to 120 nm. TEM analysis shows the size of particles in the glass-ceramics is in the range of 10 to 90 nm. The Eopt of the glass system has decreased from 2·873 to 2·606 eV, whereas in the glass-ceramic system it is observed to increase from 1·340 to 1·748 eV. Raman and infrared spectral analysis confirm the existence of various structural units such as TeO4, TeO3+1, TeO3, NbO6, NbO4, SbO3 in the glass and glass ceramic systems.The ESR spectral analysis reveals that the (Δg‖/Δg^) parameter seems to decrease from 4·444 to 2·453 in glass sytem, whereas in glass-ceramics it is observed to increase from 2·357 to 4·188. Glass transition temperature and onset crystalline temperatures are influenced by the Nb2O5 in both glass and glass-ceramic samples.