Synthesis crystallization kinetic and optical properties of europium doped tellurite nano-glass

Abstract

Tellurite glass of composition (80-x) TeO2 – 5 Na2O – 15 MgO – (x) Eu2O3, with the concentration region of 0 = x = 2.5 mol% was prepared using conventional melt-quenching technique. The transition temperature, Tg, crystallization temperature, Tc and melting temperature, Tm were determined using Differential Thermal Analysis (DTA). The glass with nano-crystalline particle was prepared by heating the as-cast glass at temperature 15 - 20 oC above the Tc. The X-Ray Diffraction (XRD) technique with the Scherrer equation was used to determine the size of nano- crystalline particle of the samples while the Scanning Electron Microscopy (SEM) technique was used to identify the formation of nano-crystalline phase. The crystallization kinetics was investigated by using DTA at various heating rate while the glass density and hardness was determined by Precisa Densitometer and Vickers microhardness, respectively. Meanwhile, the emission characteristic was evaluated using the Photoluminescence Spectroscopy (PL). The thermal analysis showed that the Tg and Tc increased with the increasing of Eu3+ content while Tm showed a break in linearity as the Eu3+ increased. The result also showed that the glass stability up to 109.29. XRD spectra confirmed the presence of nano particles with an average diameter around 68.7 nm. Meanwhile the SEM studies revealed the existence nano-crystalline morphology which was associated with the existence of crystallized phase. The influence of Eu3+ content on crystallization kinetics showed a shift of crystallization temperature peak towards a higher temperature with the increasing of heating rate as described by Kissinger and Ozawa method. The activation energy (Ea) was found to decrease from 306.9 eV to 48.9 eV with an increasing of dopant concentration. The density was found to be in the range of 5.234 to 5.334 g cm-3 while the Vickers microhardness was found to vary from 2.59 to 2.84 GPa depending on the dopant concentration. A detailed study on the luminescence spectra showed that all emission peaks for 5D0 - 7F0, 5D0 - 7F1, 5D0 - 7F2, 5D0 - 7F3 and 5D0 - 7F4 transitions were found to be around 568 nm, 600 nm, 628 nm, 664 nm and 712 nm, respectively. It was also found that the heat-treated glass and the inverse quality factor decreased with increasing Eu3+ dopant concentration.