Synthesis and characterizations of dysprosium doped zinc-sodium-tellurite glass

Abstract

Rare earth ions (REIs) doped binary and ternary tellurite glass systems are attractive because of several technological appications. Transparent tellurite glasses can be achieved by combining the vitrified tellurium oxide (TeO2) host with various modifier oxides of Zinc (ZnO), Sodium (Na2O), Silicon (SiO2), etc. over a wide composition range. Tellurite system is wellknown for large intake of REIs, excellent optical properties and low phonon energy cutoff. Determining the influence of dysprosium (Dy3+) ions doping on the improvement of physical, structural and optical properties of tellurite glasses is the main focus of this research. A series of Dy3+ ions doped zinc-sodium-tellurite glass having composition of (65-x)TeO2- 25ZnO-10Na2O-xDy2O3 (0 = x = 2.5 mol%) are prepared using melt-quenching method. Synthesized samples are characterized at room temperature via different analytical techniques. X-ray diffraction pattern verified the amorphous nature of the synthesized glass samples in the absence of any sharp crystalization peaks together with the presence of a braod hump between 25°-35° diffraction angle. Differential thermal analysis revealed good thermal stability of the glass system in the range of 120-206 °C and Hruby’s parameter between 0.47-1.33. Dy3+ ions concentration dependent density and molar volume of the glass system is found vary in the range of 5.334 gcm-3 - 5.366 gcm-3 and 24.425 cm3mol-1 - 25.273 cm3mol-1, respectively. Fourier transformed infrared spectra exhibited bonding vibrations at the wavenumber of 590-615 cm-1 and 772-817 cm-1 which are assigned to [TeO4] and [TeO3] glass network structural units, respectively. Ultraviolet-Visible-Near-Infrared (UV-Vis- NIR) spectra displayed seven absorption peaks centred at 450, 752, 801, 901, 1095, 1281, and 1687 nm which are allocated to the transitions from the ground level to the excited levels (such as 4F9/2, 6F3/2, 6F5/2, 6F7/2, 6H7/2, 6F11/2, and 6H11/2) of Dy3+ ions, respectively. The Dy3+ ions contents dependent UV-Vis absorption edge data is used to calculate various optical properties of the glass. Indirect optical band gap is decreased from 2.67-2.30 eV and the Urbach energy is increased from 0.265-0.421 eV with increasing concentration of Dy3+ ions. This indicated the enhancement of glass compactness and structural change mediated via non-bridging oxygen atoms in the network. Room temperature photoluminescence (PL) spectra showed three significant peaks centred at 497, 588, and 675 nm, which are attributed to the transitions from 4F9/2 excited state to the 6H11/2, 6H13/2, and 6H15/2 states of Dy3+ ions, respectively. Highest PL intensity enhancement of 1.54 and 1.63 for yellow and red band, respectively is obtained for glass samples with 0.8 mol% Dy3+ ions. The blue band of the sample with 1.2 mol% Dy3+ ions revealed 1.46 times PL enhancement. This enhancement is ascribed to the excited state absorption and cross-relaxation processes. Overall, it is demonstrated that the physical, structural, thermal, and optical properties of the tellurite glass is improved due to the incorporation of Dy3+ ions in the host matrix. Present optimized glass composition may be potential for the development of solid-state lasers and other photonic devices.