Band gap and polarizability of boro-tellurite glass: Influence of erbium ions

Abstract

Understanding the influence of rare earth ions in improving the structural and optical properties of inorganic glasses are the key issues. Er 3+-doped zinc boro-tellurite glasses with composition 30B 2O3-10ZnO-(60-x) TeO2-xEr2O 3 are prepared (x = 0, 0.5, 1, 1.5 and 2 mol%) using melt quenching technique. The physical and optical characterizations are measured by density and UV-Vis-IR absorption spectroscopy. The color of the glass changed from light yellow to deep pink due to the introduction of Er3+ ions. The maximum density is found to be ∼4.73 g cm-3 for 1 mol% of Er 3+ doping. The variations in the polarizability (6.7-6.8 cm 3) and the molar volume (27.987-28.827 cm3 mol -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 direct and indirect optical band gaps are increased while the phonon cut-off wavelength and Urbach energy decreased with the increase of erbium content. A high density and wide transparency range in VIS-IR area are achieved. Our results on high refractive index (∼2.416) and polarizability suggest that these glasses are potential for photonics, solid state lasers and communications devices.