Md. Rahim Sahar

TeO2–ZnO–ZnCl2 glasses for IR transmission

Abstract Glasses based on TeO2–ZnO–ZnCl2 have been made successfully. Their transmission properties have been studied using FTIR, while DTA has been applied to determine their thermal properties. It is found that these glasses exhibit transmission beyond 6 μm and possess thermal stability up to 140°C. The corrosion rate was found to be around 10−5 g d−1 cm−2.

Surface enhanced Raman scattering and plasmon enhanced fluorescence in zinc-tellurite glass

We report significant enhancements in Er(3+) luminescence as well as in Raman intensity in silver nanoparticles embedded zinc-tellurite glass. Surface enhanced Raman scattering effect is highlighted for the first time in tellurite glass containing silver NPs resulting in an enhanced Raman signal (~10 times). SAED manifest the growth of Ag(0) nanoparticles along the (111) and (200) crystallographic planes having average diameter in the range 14-36 nm. Surface plasmon resonance bands are observed in the range 484-551 nm. Furthermore, four prominent photoluminescence bands undergo significant enhancements up to 3 times. The enhancement is majorly attributed to the local field effect of silver NPs.

Oxychloride glasses based on the TeO2-ZnO-ZnCl2 system

Abstract A series of glasses based on the TeO2-ZnO-ZnCl2 system was prepared and their physical, thermal and optical propeties were investigated. This system provides a wide and stable glass formation range in which a Tc-Tg gap beyond 140°C can be achieved. An infrared cut-off edge up to 6.5 μm can be obtained, while the optical energy gap was found to be in the range of 2.0–2.5 eV. Most properties are observed to be dependent in a systematic manner on the ZnCl2 content.

Spectral investigation of Sm3+/Yb3+co-doped sodium tellurite glass

Sm 3+ /Yb 3+ co-doped tellurite glasses are prepared by melt-quenching technique. The density of the glasses varies between 4.65 and 4.84 g/cm 3 . The optical absorption spectra consist of eight bands in the wavelength range of 350-2 000 nm, which correspond to the transitions from ground level 6 H 5/2 to the various excited states of the Sm 3+ ion. Energy band gaps vary in the range of 2.73-2.91 eV, and the Urbach energy ranges from 0.21 to 0.27. Emission spectra exhibit four peaks originating from the 4 G 5/2 energy level centered at 576, 613, 657, and 718 nm. Quenches in emission bands may be due to the energy transfer from the Sm 3+ to Yb 3+ ions.

Optical Investigation of Sm3+ Doped Zinc-Lead-Phosphate Glass

Samarium doped lead-zinc-phosphate glasses having composition (60−x)P2O5-20PbO-20ZnO-xSm2O3 where x=0, 0.5, 1.0, 3.0mol% were prepared by using the melt quenching technique. The Archimedes method was used to measure their densities, which are used to calculate the molar volumes. The values of densities lie in the range 3.698–4.090 gm/cm3 whereas those of molar volume lie in the range of 37.24–40.00 cm−3. UV-vis-NIR absorption spectroscopy in the wavelength range 200–2000 nm was carried out. Absorption spectra consist of seven absorption peaks corresponding to the transitions from the 6H5/2 ground state to various excited energy levels. The energy band gap measured from the optical absorbance is found to be in the range of 3.88-4.43 eV and 3.68-4.33 eV for direct and indirect transitions, respectively. In addition, the photoluminescence spectrum shows four prominent emission bands centered at 560, 597, 642 and 700 nm corresponding to the 4G5/2−6HJ (J=5/2, 7/2, 9/2, 11/2) transitions respectively and the intensity of all the bands are enhanced as the concentration of Sm3+ ions increases.

Properties of SnO2-based ceramics

Some SnO2-based ceramics of the ternary and binary systems SnO2-Sb2O3-CuO have been prepared and some of their properties have been measured. It was observed that most of their properties, which include density, porosity, d.c. electrical conductivity, as well as the crystal occurrence, were dependent on the presence of CuO. Crystal phase occurrence was investigated using the X-ray diffraction technique and it was found that the phases were predominantly SnO2 and Sb2O4 crystals. The d.c. conductivity at different sintering temperatures was found to be enhanced by the simultaneous presence of Sb2O3 and CuO.

Chemical durability of oxychloride glasses

The chemical durability of some oxychloride glasses from the system Sb2O3PbCl2ZnCl2 was studied. It was observed that the corrosion is a diffusion controlled process which is strongly dependent on the availability of chlorine in the glass.

Plasmon-Enhanced Upconversion Fluorescence in Er3+:Ag Phosphate Glass: the Effect of Heat Treatment

The melt quenching method is used to prepare erbium-doped silver nanoparticle (NP) embedded phosphate glass. The effect of annealing on the glass on the formation of silver NPs produced by the reduction of silver (Ag+ →Ag°) is studied. The glass samples are characterized by x-ray diffraction, UV-vis-NIR absorption, photoluminescence spectroscopy and transmission electron microscopy (TEM) imaging. The absorption spectra reveal not only the peaks due to Er3+ ions, but also the surface plasmon resonance band of silver NPs located around ~442 nm. The TEM imaging shows the homogeneous distribution of silver NPs of almost spherical shape with an average diameter of ~5 nm. Upconversion luminescence spectra show two major emissions at 550 and 638 nm, originating from the 4S3/2 and 4F9/2 energy levels of the Er3+ ions, respectively. The enhancement in the luminescence intensity of both the green and red bands is found to be due to the effective local field of the silver NPs as well as the energy transfer from the nanoclusters, comprised of centers with silver ions bound to silver atoms in dimers or trimers to Er3+ ions, whereas quenching occurred due to the energy transfer from erbium ions to silver NPs (Er3+ →Ag°).

An Insight into the Structural, Electronic and Transport Characteristics of XIn2S4 (X = Zn, Hg) Thiospinels using a Highly Accurate All-Electron FP-LAPW+Lo Method

The highly accurate full-potential linearized augmented plane wave plus local orbital method is employed to calculate the structural, electronic and transport properties of HgIn2S4 and ZnIn2S4. For ZnIn2S4, the calculated In—S bond length is in good agreement with the experimental data. Bulk moduli results suggest that ZnIn2S4 can afford more compressional effects than HgIn2S4. The present study confirms that both HgIn2S4 and ZnIn2S4 are indirect band gap materials with band gap values of 0.705 eV and 1.533 eV respectively. The localized region existing in the most bottom valance band of both materials splits into states by 1 eV energy difference under the spin orbital coupling effect. Contour plots of charge density predict that chemical bonding in these compounds is a mixture of ionic and covalent characteristics. Effective mass results reveal that mobility of charge carriers in ZnIn2S4 is greater than that in HgIn2S4.

Interrelation of intrinsic defects and optical absorption properties of lithium niobate (LiNbO3) crystals

The optical absorption of pure lithium niobate (LiNbO3) single crystals were measured from the ultraviolet to the visible range with the incident light being parallel to the z axis of the crystals. The wavelength dependence of the absorption coefficient α and its root α1/2 (α versus hν and α1/2 versus hν, respectively) were calculated and the characteristics of the absorption edges were discussed. The absorption edges below 3.6 eV of all samples are attributable to indirect transition. The energy gap Eg and E′g of the crystals, which correspond to the direct transition and the indirect transition, respectively, and the energy of phonons Ep taking part in the indirect transition were calculated. It was found that the energy band structure depends on [Li]/[Nb] ratio of lithium niobate crystals. The change of E′g may be attributable to the distortion of energy band structures resulting from the intrinsic defects.