Papers by Author: M. Rahim Sahar

Abstract: . The study of the crystallization kinetics of rare-earth doped glass stimulated much interest especially for crystallization process. In this work transparent Eu2O3 doped glasses with composition TeO2 - Na2O – MgO were prepared using conventional melt-quenching technique. The amorphous nature of glass was confirmed using X-ray diffraction method. The influence of Eu3+ content on the crystallization kinetics of the glass such as activation energy (Ea) was thoroughly evaluated under non-isothermal conditions using DTA. The crystallization kinetic at different heating rate from 5 °C min-1 to 25 °C min-1 at different crystallization temperature (Tp) were examined and verified using Ozawa method. The result showed that the activation energy (Ea) was decreased with the increasing of the dopant concentration from 319.8 eV to 93.5 eV.

Abstract: Nanoparticles (NPs) size dependent enhancement of the infrared-to-visible frequency up-conversion (UC) and absorption coefficient in silver NPs embedded Er3+ doped tellurite glasses on pumping with the 976 nm radiation are investigated. Rate equations are derived by developing a comprehensive 4-level model in integrating the effects of quantum confinement and local field of silver NPs. Considering the spherical NPs size distribution as Gaussian, an analytical expression for the luminescence intensity and absorption coefficient are obtained for the first time. An enhancement in UC emission intensity of the green bands (2H11/2→4I15/2 and 4S3/2→4I15/2) and red band (4F9/2→4I15/2) emission of Er3+ ion at temperature 250 K and at optimized Er3+ concentration 1.0 mol% is observed up to few times in the presence of silver NPs. Furthermore, the green emission shows larger enhancement than the red emission. The observed of Er3+ luminescence is mainly attributed to the local field effects namely the surface plasmon resonance of silver NPs that causes an intensified electromagnetic field around NPs, resulting in enhanced optical transitions of Er3+ ions in the vicinity. The model is quite general and can be applied to other rare earth doped glasses containing metallic NPs. Our results on NPs size dependent emission intensity and absorption coefficient are in conformity with other findings. The present systematic study provides useful information for further development of UC lasers and sensors.

Abstract: Series of glass based on (80-x)TeO2-10PbO-10PbCl2-xYb2O3 where 0.0 ≤ x ≤ 3.0 has been successfully prepared by melt quenching technique. The amorphous nature of glass has been determined by X-ray diffraction method. Their corrosion behavior was investigated using the FTIR spectroscopy technique on the sample that has been immersed in distilled water and in aqueous solution of pH 4 and pH 9 for 10 days. There were three major absorption peaks around 3600 cm-1, 889 cm-1 and 470 cm-1 has been observed. The intensity of each peak was found to vary with the Yb3+ content.