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The influence of yttrium-ions on the optical and electrical behavior of PVA polymeric films
摘要： The polyvinyl alcohol (PVA) films doped with various wt% of yttrium nitrate salt were synthesized by standard solution casting technique in order to examine the functional electrical and optical properties. The degree of the crystalline structure that evaluated in the films were investigated by x-ray diffraction and Fourier transform infrared spectroscopy measurements. In addition, the surface images have been obtained via scanning electron microscopy (SEM). The optical parameters have been calculated from UV–visible-NIR transmittance spectroscopy. Also, the dielectric constant measurement and the DC resistance that are arisen in the PVA films with different wt% of Y3+ have been done. All the samples show semi-crystalline phases. The average size, of the cluster Y3+ in the SEM images, increase to 1.63 μm for PVA/37 wt% Y3+ sample. Therefore, the optical absorption of this sample is higher than the others. The value of the energy gap decrease from 5.11 eV to 4.47 eV for PVA/0.037 wt% Y3+ and PVA/37 wt% Y3+ samples, respectively. The nonlinear current—voltage behavior, at high applied voltage, of the polymeric films, is observed with different values of slope, which is a characteristic of the varistor materials. So, these films could be used in different applications like optoelectronic and varistor devices.
关键词： Varistor,Dielectric,XRD/FTIR,SEM,Optical energy gap,Y3+-doped PVA
更新于2025-09-23 15:22:29
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Luminescence of Phosphate Glasses: P2O5-ZnO-BaF2-K2TeO3-Al2O3-Nb2O5 Doped with Sm3+ Ions for Display and Laser Material
摘要： Luminescent phosphate glasses having the composition 40P2O5-30ZnO-20BaF2-3.8K2TeO3-1.2Al2O3-5Nb2O5 in mol.% doped with 3 9 103 ppm and 4 9 103 ppm Sm2O3 were successfully prepared by a melt-quenching technique. The investigated glasses were characterized by x-ray diffraction, UV–visible–NIR, absorption, emission, and ?uorescence lifetime analysis. The radiative properties were calculated using Judd–Ofelt (J–O) spectral intensity parameters for each of the glasses, which revealed the following trend: X2 > X4 > X6. The J–O intensity parameters were used to evaluate the spontaneous emission properties including branching ratios, transition probabilities, and radiative lifetime. The value of the optical energy band gap was found to decrease with an increase in Sm3+ content, which is explained on the basis of structural changes. The calculated stimulated emission cross-section studied was high, and increased from rSE; at 1.62 lm of glasses 3.81 9 10(cid:2)21 cm2 to 4.38 9 10(cid:2)21 cm2 with increasing Sm3+ ion concentration. The structure of the glasses was investigated by computing Internuclear (cid:3) and ?eld strength F( ) and measurement of Raman spectra.
关键词： refractive index,UV–Vis–NIR,Judd–Ofelt analysis,emission cross-section,Raman spectra,Oxide glasses,density,optical energy gap
更新于2025-09-23 15:21:01
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Influence of cobalt-doping on the optical properties of zinc tris–thiourea sulfate (ZTS) single crystal
摘要： Zinc tris-thiourea sulfate (ZTS) single crystals, pure and doped with different concentrations of cobalt, were synthesized and grown by the slow evaporation technique of supersaturated aqueous solutions at 315 K. Co2+ concentration in the solution was 2, 4 and 6 mol%. Optical transmittance was measured for the obtained crystals as a function of wavelength in the range of 190–900 nm. The present investigation shows that doping ZTS crystal with Co2+ changes the values of optical transmittance, cut off wavelength, absorption coefficient of ZTS crystal exhibits an exponential dependence on photon energy following Urbach relation. Doping ZTS crystal with Co2+ modifies its optical properties. The absorption coefficient, optical energy gap, Urbach tail energy and steepness parameter. The changes are systematic i.e. the mentioned optical parameters increase or decrease continuously with increasing Co2+ concentration in the growth solution. The electrical conduction of ZTS crystal is increased with cobalt doping. The Urbach tail energy changes reversely with the optical energy gap.
关键词： ZTS crystal,cobalt-doped,urbach tail energy,optical energy gap,steepness parameter
更新于2025-09-10 09:29:36
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Synthesis and Characterization of BaAl2O4 Catalyst and its Photocatalytic Activity Towards Degradation of Methylene Blue Dye
摘要： Hexagonal BaAl2O4 catalyst has been prepared using a gamma-ray irradiation assisted polyacrylamide gel method. The catalysts synthesized at different calcining temperatures were analyzed to insight into their effects on the structural, crystalline, surface morphology, color, optical, fluorescence and photocatalytic properties of the hexagonal BaAl2O4 catalyst. Increasing the calcining temperature has obvious influences on the crystallinity, color, optical properties and the formation of the hexagonal BaAl2O4 catalyst. The optical energy gap (Eg) value of the hexagonal BaAl2O4 catalyst increases with the increasing of calcining temperature. TEM image of the pure hexagonal BaAl2O4 catalyst shows a morphology of flake structure and aggregation. Raman spectroscopy of the pure hexagonal BaAl2O4 catalyst exhibits four luminescent background peaks at 400, 415, 428 and 445 nm mainly due to the oxygen vacancies (VO), Ba vacancies (VBa) and some color centers exists in the BaAl2O4 sample. A comparison of photocatalytic activity among samples for degradation of methylene blue (MB) dye indicates that the pure hexagonal BaAl2O4 catalyst exhibits highest photocatalytic activity under the irradiation of both visible and ultraviolet light. Based on the fluorescence experiment, electrochemical and active species tests, the high photocatalytic activity of the pure hexagonal BaAl2O4 catalyst to be related to hole (h+) and hydroxyl radical (·OH) and also to the defects in the sample.
关键词： BaAl2O4,photocatalytic activity,methylene blue,polyacrylamide gel method,calcining temperature,optical energy gap
更新于2025-09-10 09:29:36
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Fabrication and analysis of the structural phase transition of ZrO <sub/>2</sub> nanoparticles using modified facile sol–gel route
摘要： The synthesis of zirconia nanoparticles is achieved through a modified facile sol–gel route. The as-prepared gel is analyzed thermally using TGA and DTA techniques to spot the crystallization process of zirconia nanoparticles. The prepared gel is then annealed at different temperatures and the structure was found to change between tetragonal and monoclinic crystal systems. The first stable tetragonal phase is achieved after annealing for 2 h at 400°C. The annealed powders between 600°C and 800°C demonstrate mixed tetragonal/monoclinic phases. Annealing at 1000°C and higher temperatures up to 1200°C resulted in pure monoclinic phase. Cubic phase was not detected within the annealing temperature range in this study. The elemental analysis of the annealed powder confirmed the formation of zirconia nanoparticles with the chemical formula ZrO2. The FTIR spectra of the annealed samples introduced a variation in the vibrational bands especially around the phase transition temperature. HR-TEM images reported the formation of nano-zirconia crystals with apparently large particle sizes. The optical energy gap of zirconia nanoparticles is investigated and determined.
关键词： ZrO2 nanoparticles,HR-TEM,sol–gel synthesis,EDAX,optical energy gap
更新于2025-09-09 09:28:46