Papers by Keyword: UV-VIS-NIR

Abstract: Bismuth glasses have been prepared from a commercial-grade chemical glass mixture doped with potassium chromate in different contents. They have been melted at 1250 °C for 4 h, quenched in a metal plate, and annealed at 500 °C for 20 min. The surface morphology of glass samples has been examined using scanning electron microscopy (SEM). The dielectric properties have been investigated. UV-Vis-NIR absorption has been analyzed. The results show the growth of microcrystal precipitated in the glass matrix, and colors of glass change from colorless to green and opaque with the increasing content of potassium chromate. The density of glass decreases with the increasing content of potassium chromate. The UV-Vis spectra show strong absorption of UV. The chromium-doped glasses not only absorb the UV but also the violet and/or blue lights which depend on the chromium contents.

Abstract: Au NPs contents dependent modifications in the absorption and bonding parameters are inspected. Glass systems with composition (79-y)TeO₂ – 15PbO – 5PbCl₂ – 1Er₂O₃ – (y)AuCl₃ where 0.0 ≤ y ≤ 0.1 mol% are prepared and characterized using X-ray Diffraction (XRD). The absorption characteristics of the glass are observed using UV-Visible-NIR (UV-VIS-NIR) spectrophotometer. XRD spectra confirm the amorphous nature of all samples. UV-VIS-NIR spectra reveal seven absorption bands centered at about 490, 526, 551, 652, 800, 982 and 1520 nm originating from ⁴I_15/2 to ⁴F_7/2, ²H_11/2, ⁴S_3/2,⁴F_9/2, ⁴I_9/2, ⁴I_11/2 and ⁴I_13/2 transitions, respectively. The low value of indicated an increase in the covalency and the positive sign of for all glass systems indicates the bonding between the RE ions and the surrounding ligand is covalent in nature.

Abstract: Tellurite glass containing zirconium fluoride (ZrF₄) with composition of (90-x)TeO₂-10MgO-(x)ZrF₄,where 0.0 ≤ x ≤ 6.0 in mol% has successfully been prepared by melt quenching technique. X-Ray Diffraction (XRD) pattern verified the amorphous nature of the glass. In this study, the physical and optical properties were investigated in term of density and absorption properties by using Archimedes method and UV-Vis Spectroscopy. It was found that glass density decreases in the range of 4.842 – 4.995 g cm^-3 with the increase of ZrF₄ concentration. Meanwhile, the molar volume is increased in the range from 29.566 to 30.593 cm³/mol with increase of ZrF₄. The absorption edge is found to shift toward a higher wavelength as the ZrF₄ concentration is increased. On the other hand, the optical energy band gap shows the decrement from 2.573 to 2.212 eV for indirect transition and from 3.044 to 2.927 eV for direct transition with the addition of ZrF₄ concentration while the Urbach energy, increases from 0.302 to 0.498 eV with the increase of ZrF₄. All the results will be discussed with respect to the glass composition.

Abstract: Glasses with chemical composition of (60-x)P₂O₅-25ZnO-(15+x)Li₂O with 0.0 ≤ x ≤ 5.0 mol % are prepared by melt quenching technique. The physical properties, by mean of density and molar volume are determined. The amorphous nature, absorption and structural behaviour are characterized using X-ray Diffraction (XRD), Ultraviolet-visible-near infrared (UV-Vis-NIR) and Fourier transform infrared (FTIR) respectively. In this work, the glass densities are found increases in the range of 2.70 - 2.78 gcm^-3 and molar volume decreases from 37.48 - 40.75 gcm^-3 with respect to Li₂O concentration. Meanwhile, the optical band gap energy for direct and indirect transition are found decreases from 3.074 eV to 2.525 eV and 2.699 eV to 1.670 eV respectively. The Urbach energy is varies as Li₂O content increases. The refractive index of these glasses is ranging from 2.48 to 2.90. FTIR spectra exhibited seven bands which centered at 512 cm⁻¹, 767 cm⁻¹, 918 cm⁻¹, 1087 cm⁻¹, 1281 cm⁻¹, 1627 cm⁻¹ and 3441 cm⁻¹ wavenumber that assigned as vibration of Zn-O, symmetric stretching vibration of P-O-P rings, asymmetric stretching vibration of P-O-P groups, asymmetric stretching of PO2-group, asymmetric stretching vibration P=O, bending vibration of water molecule and fundamental stretching of hydroxyl group.

Abstract: Many trivalent rare earth ions such as Er³⁺, Tm³⁺, Ho³⁺, Pr³⁺ and Nd³⁺ were doped as absorption and emission centers in glass hosts. In this work, lead borotellurite (PBT) glass doped with neodymium ion (Nd³⁺) has been prepared and characterized by mean of their optical properties. The UV-Vis measurement has been carried out in order to determine the optical band gap energy, reflective indices and the polarizability. Optical absorption spectra of the glass samples are recorded in the range 400–900 nm at room temperature From the result, there are six significant absorption peaks that corresponds to 525 nm, 584 nm, 683 nm, 747 nm, 805 nm and 878 nm wavelength have been observed with the most predominant peak to be used as excitation wavelength is found centered at 584 nm. The energy band gaps as well as the refractive indices were found to vary from 2.50eV to 2.59eV and from 1.89 to 1.96 with mol% of Nd content respectively. Meanwhile, the polarizability shows a similar trend of results to refractive indices as it varies from 5.56 x 10^-24 cm³ to 5.63 x 10^-24 cm³. These results will be discussed further in details.

Abstract: Keywords: Tellurite Glass, UV-Vis-NIR, absorption, Urbach energy. Abstract: To improve the optical behaviour of Lithium Niobate Tellurite glass with rare- earth dopant are the important issue from application and device perspectives. Er³⁺ and Nd³⁺ doped tellurite glasses of molar composition (70-x-y)TeO₂ – 15Li₂CO₃ – 15Nb₂O₅ – xEr₂O₃ – yNd₂O₃ system (x = 0 mol % and 1.0 mol %) (0 mol % ≤ y ≤ 1.0 mol %) have successfully been made by using melt quenching technique. The physical properties of the glass sample are obtained. From Ultraviolet- Visible- Near Infrared (UV-Vis-NIR) Spectroscopy, it is observed that the spectrum consists absorption peaks which corresponded to transitions from both ground state of Erbium, ⁴I_15/2 to the excited state of ⁴I_15/2, ⁴I_13/2, ⁴I_3/2, ⁴I_11/2, ²H_9/2, ⁴I_9/2, ²H_11/2, ⁴S_3/2, ²H_11/2 and ⁴F_7/2 respectively and Neodymium, ⁴I_9/2 to the excited state of ⁴I_15/2, ⁴I_15/2, ⁴I_3/2, ⁴F_9/2, ²G_7/2, ²G_9/2 and ²G_11/2 respectively. The indirect band gaps obtained from the above dependence are the interband transitions, but later it involves the phonon interaction where the values of indirect optical band gaps lie between 2.84 eV to 3.12 eV as the Nd₂O₃ content increase. The Urbach energy for the glass system decreases from 0.31 eV to 0.21 eV as the Nd₂O₃ content increase.

Abstract: Single crystals of pure and thiourea substituted L-alanine single crystals were grown successfully by the solution method with slow evaporation technique at room temperature. The effect of dopant on crystal properties has been studied. The solubility of the grown samples was found at various temperatures. Structural characterization of the grown crystals was determined by the single crystal X-ray diffraction (XRD). EDAX studies indicate the presence of thiourea in the doped L-alanine crystals. The functional groups were identified by FTIR spectroscopy. The UV-Vis- NIR spectral studies were carried out to analyze the optical absorption of the grown crystals and found that the absorption is very low in the wavelength region 232-1000nm for both the samples. SEM studies explain the surface morphologies of the grown crystals. Improvement in the SHG efficiency was studied by the Kurtz and Perry method. Thermal analysis has been carried on the grown crystal. Keywords: NLO, XRD, EDAX, UV-Vis-NIR, SEM

Abstract: Gallium Phosphide (GaP) nanostructures were grown on p-Si substrates by Metal Organic Chemical Vapor Deposition (MOCVD) to study the structure of low dimensional IIIV semiconductor on Si substrates. It is found that at a temperature of 540 °C, nanostructures with diameter 4080 nm and height 515 nm were obtained. The density of the nanostructures was found to be 10¹⁴ m^-2. The UV-Vis-NIR spectra showed a blue shift of band gap. Photoluminescence measurements also confirmed the band gap enhancement.

Abstract: Single Crystal of γ-glycine lithium nitrate with non-linear optical material have been grown by slow evaporation method at room temperature. Structural and Crystalline nature of the grown γ-glycine lithium nitrate crystal was confirmed by powder X-ray diffraction technique. UV-Visible transmittance study was performed to analyze optical transparency of γ-glycine crystal and found that the crystal was transparent in the entire visible region. The mechanical properties of the grown crystal was subjected to Vickers hardness test and the Brittleness index (Bi), Fracture toughness (Kc), Elastic stiffness constant (C11) were estimated.

Abstract: A wet non-conventional method for preparing aluminophosphate glasses is presented. Aluminophosphate glasses belonging to the oxide system Li2O-BaO-Al2O3-La2O3-P2O5, doped with rare-earth ions (Pr3+, Er3+, Gd3+, and Yb3+) were obtained. The influence of the doping ions on the optical properties of the phosphate glasses has been investigated in relation with micro-structural and local electronic phenomena The optical behavior of Li2O-BaO-Al2O3-La2O3-P2O5 glasses doped with 3% mol. rare-earth ions has been studied by ultra-violet-visible-near-infra-red (UV-VISNIR) spectroscopy. The transmission spectra revealed electronic transitions between 4f and 6s inner orbital of the rare-earth ions. Structural information via optical phonons was provided by infra-red (IR) absorption spectra in the range 400-4000 cm-1. IR optical phonons are characteristic for the vitreous phosphate network, showing out the glass network-forming role of P2O5. The absorption spectra present the main PO2 and P-O-P symmetrical stretch modes besides P-O-P bend mode, P-OH, P=O, PO3 2-, asymmetrical and symmetrical vibration modes. Fluorescence spectra of the rareearth- doped aluminophosphate glasses, in the visible range, were obtained by laser excitation at 514.5 nm. The fluorescence signals revealed specific electronic transitions, which provide visible and near-infra-red emission. Glasses containing rare-earth ions exhibit luminescence at the following wavelengths: Pr3+ ions at 820 nm and 880 nm, Er3+ ions at 520 nm, 550 nm and 560 nm, Gd3+ ions at 530 nm, 540 nm, 550 nm 820 and 880 nm, Yb3+ions at 530 nm, 540 nm, 550 nm and 980 nm.