Synthesis and optical properties of Co2+ and Ni2+ ions doped β-BaB2O4 nanopowders

Co²⁺ and Ni²⁺ ions doped β-BaB₂O₄ nanopowders have been prepared by co-precipitation method and their structural properties are studied by spectroscopic techniques. Powder XRD data reveals that the crystal structure belongs to monoclinic and the average crystallite size is calculated. Optical absorption spectra data reveal octahedral site symmetry for Co²⁺ and Ni²⁺ ions. Crystal field (Dq) and inter-electron repulsion (B and C) parameters are evaluated for Co²⁺ doped β-BaB₂O₄ nanopowders as Dq=960, B=900 and C=3850 cm^?1 and for Ni²⁺ doped β-BaB₂O₄ nanopowders, Dq=900, B=850 and C=3500 cm^?1. FT-IR spectra showed the characteristic vibrational bands related to BO₃ and BO₄ molecules. Photoluminescence spectra contain the emission bands in ultraviolet and blue regions.     

Synthesis by sol–gel process,structural and optical properties of nanoparticles of zinc oxide doped vanadium

We report the elaboration of vanadium-doped ZnO nanoparticles prepared by a sol–gel processing technique. In our approach, the water for hydrolysis was slowly released by esterification reaction followed by a supercritical drying in ethyl alcohol. Vanadium doping concentration of 10 at.% has been investigated. After treatment in air at different temperatures, the obtained nanopowder was characterised by various techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and photoluminescence (PL). Analysis by scanning electron microscopy at high resolution shows that the grain size increases with increasing temperature. Thus, in the case of thermal treatment at 500 °C in air, the powder with an average particle size of 25 nm shows a strong luminescence band in the visible range. The intensity and energy position of the obtained PL band depends on the temperature measurement increase. The mechanism of this emission band is discussed.     

Synthesis and properties of MoO3–V2O5–PbO glasses

Lead vanadate glasses of the system xMoO₃–50V₂O₅–(50-x)PbO (0 ≤ x ≤ 25 mol. %) were synthesized and studied by FTIR and ultrasonic spectroscopy and differential scanning calorimetry to investigate the role of MoO₃ content on their atomic structure. The elastic properties and Debye temperatures of the glasses were investigated using sound velocity measurements at 4 MHz. The activation energy for the glass transition was derived from the dependence of the glass-transition temperature (T_g ) on the heating rate. Similarly, the activation energy of the crystallization process was also determined. According to the IR analysis, the vibrations of the vanadate structural units are shifted towards higher wavenumbers on the formation of bridging oxygens. The change of density and molar volume with MoO₃ content reveals that the molybdinate units are less dense than the lead oxide units. The observed compositional dependence of the elastic moduli is interpreted in terms of the effect of MoO₃ on the coordination number of the vanadate units. A good correlation was observed between the experimentally determined elastic moduli and those computed according to the Makishima–Mackenzie model. It is assumed that MoO₃ plays the role of a glass former by increasing the activation energy for the glass transition and the activation energy for crystallization and by increasing both the thermal stability and the glass formation range of the vanadate glasses.     

Effects of heat treatment and TiO2 content on the optical properties of Eu3+ doped TiO2–SiO2 thin films

The photoluminescence properties of Eu³⁺-doped TiO₂–SiO₂ thin films were investigated. The films were deposited on silicon substrates by the sol–gel process using the dip-coating method. The molar ratio of TiO₂ content was varied from 25% to 100%, while Europium concentration was fixed to 1%. The obtained films were calcinated at various temperatures ranging from 400 °C to 1300 °C, which allowed determining the optimal conditions for the Eu³⁺ luminescence. Meanwhile, the structure of TiO₂–SiO₂ powders, prepared in the same conditions as the films, was also studied by Raman spectroscopy. It revealed the role of Europium and SiO₂ on the stabilization of the anatase phase and the importance of the silica matrix in the control of titania particle size.     

Effect of Fe3+ doping on structural,optical and electrical properties δ-Bi2O3 thin films

Fe³⁺ doped δ-Bi₂O₃ thin films were prepared by sol–gel method on quartz glass substrate at room temperature and annealed at 800 °C. The thin films were then characterized for structural, surface morphological, optical and electrical properties by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), optical absorption measurements and d.c. two-probe, respectively. The XRD analyses revealed the formation δ-Bi₂O₃ followed by a mixture of Bi₂₅FeO₄₀ and Bi₂Fe₄O₉. SEM images showed reduction in grain sizes after doping and the optical studies showed a direct band gap which reduced from 2.39 eV for pure δ-Bi₂O₃ to 1.9 eV for 10% Fe³⁺ doped δ-Bi₂O₃ thin film. The electrical conductivity measurement showed the films are semiconductors.     

Spectral dispersion of linear optical properties for Sm2O3 doped B2O3–PbO–Al2O3 glasses

Glasses having composition (B₂O₃)₂₅ (PbO)₇₀ (Al₂O₃)₅ (Sm₂O₃)_x ,where x=0, 0.5, 1, 2, 3 and 5 g were prepared using the normal melt quench technique. Spectral reflectance and transmittance at normal incidence of the glass samples are recorded with a spectrophotometer in the spectral range 220–2200 nm. These measured values are introduced into analytical expressions to calculate the real and imaginary parts of the refractive indices. Wemple–DiDomenico single oscillator model and one-term Sellmeier dispersion relations are used to model the real refractive indices. Dispersion parameters such as: single oscillator energy, dispersion energy, lattice oscillating strength, average oscillator wavelength, average oscillator strength and Abbe's number are deduced and compared. Absorption dispersion parameters such as: Fermi energy, optical energy gap for direct and indirect transitions, Urbach energy and steepness parameter are calculated. Effects of doping Sm₂O₃ on these linear optical parameters are investigated and interpreted.     

Structural and optical properties of WO3–PbO–B2O3 glass-ceramic

The WO₃–PbO–B₂O₃ glasses and glass ceramics are prepared and investigated with the help of XRD, density, molar volume, UV–visible and FTIR spectroscopy. XRD pattern reveals the glassy behavior up to 4% concentration of WO₃ and ceramic behavior of the prepared samples with concentration of WO₃ >4%. Band gap of glass samples decreases with increase in the WO₃ concentration from 0–5%. The samples with WO₃ concentration >5% do not respond to UV–visible absorption. The density and molar volume measurements show the compaction of structure of the samples, which is due to the formation of BO₄ groups. FTIR spectroscopy shows the formation of BO₄ group and W–O–W bending vibration at high concentration of WO₃.     

Reddish-orange Ca3−xAl2O6:xEu3+ nanophosphors: Fast synthesis and photophysical properties

This paper focuses on the synthesis and the photoluminescent properties of Ca_3−xAl₂O₆:xEu³⁺ (0≤x≤0.1) nanophosphors prepared by microwave-assisted combustion method without any further heat treatment. X-ray diffraction, scanning electron microscopy and photoluminescence spectroscopy were used to characterize the produced samples. Nanosized particles smaller than 120 nm were obtained as confirmed by SEM. When exposed to UV light radiation at 254 nm, the europium-doped nanoparticles showed strong reddish-orange luminescence due to the characteristic transitions ⁵D₀→⁷F₁ (orange) and ⁵D₀→⁷F₂, (red). The maximum emission intensity of the visible emission was obtained for x=0.05. It was also found that higher doping concentrations led to the luminescence quenching by a cross-relaxation mechanism between Eu³⁺ ions in the lattice.     

Effect of 100 MeV O7+ ion beam irradiation on structural,optical and electronic properties of SnO2 thin films

In this paper, we present the impact of swift heavy ion beam irradiation on the structural, optical and electronic properties of SnO₂ thin films. Thin films were deposited using the pulsed laser deposition technique on Al₂O₃ substrates. Atomic force microscopy, X-ray diffraction, UV–visible absorption and temperature-dependent resistivity measurements were performed to explore the morphological, structural, optical and electronic properties of the as-deposited and irradiated samples. The peak intensity of the (200) peak was found to decrease monotonously with increasing irradiation fluence. The band gap energy of the 1×10¹¹ ion/cm² irradiated sample was found to increase. The electrical resistivity of the samples showed a continuous increase with the irradiation fluence.     

Optical,thermal, and structural properties of Nb2O5–TeO2 and WO3–TeO2 glasses

Glass samples from two systems, Nb₂O₅–TeO₂ and WO₃–TeO₂, were prepared at two melt quenching rates and characterized by density, DSC, UV-visible, and Raman spectroscopy. Addition of Nb₂O₅ decreased the density while increase in the WO₃ concentration increased the density. Glasses prepared at higher quenching rates had smaller densities than glasses of the same composition prepared at lower quenching rate although the short-range structure of both glasses were identical, as revealed by Raman spectroscopy. Optical studies found an intense absorption band just below the absorption edge in both the glass series. This band was attributed to electronic transitions of Nb⁵⁺ and W⁶⁺ ions and a lone pair of electrons on Te atoms. Glass transition temperature increased with increase in Nb₂O₅ and WO₃ mol% due to the increase in average bond strength in the glass network. Raman spectroscopy showed that the concentration of TeO₄ units decreased with the increase in Nb₂O₅ and WO₃ concentrations.     

Dy3+ doped SiO2–B2O3–Al2O3–NaF–ZnF2 glasses: An exploration of optical and gamma radiation shielding features

A series of Dy³⁺ doped zinc-aluminoborosilicate glasses with chemical composition 30SiO₂-(30-x) B₂O₃–10Al₂O₃–15NaF–15ZnF₂-xDy₂O₃ (x = 0, 0.5, 0.7, 1.0 and 1.5 mol %) were prepared by conventional melt-quenching method. Structural and optical properties of the glasses were analyzed through XRD, FTIR, UV–Visible–NIR and luminescence studies. Gamma radiation shielding parameters were obtained using PSD software. Nephelauxetic ratio (β) and bonding parameters (δ) calculated using absorption spectrum shows the decreasing ionic nature of the Dy ions. Judd-Oflet parameters (Ω₂, Ω₄ and Ω₆) obtained shows the covalency and asymmetric nature of dysprosium ions. The luminescence properties shows that Dy³⁺ doped glasses have two strong intense emission at blue (482 nm) and yellow (575 nm) region. Branching ratio and stimulated emission cross section calculated suggests the glasses suitability to act as lasing material. CIE colour coordinates and its colour correlated temperature (CCT) for the glasses were estimated and found that these prepared glasses lie in the warm white light region.     

Synthesis, structural, optical and electrical properties of metal nanoparticle–rare earth ion dispersed in polymer film

Cu-nanoparticles have been prepared by ablating a copper target submerged in benzene with laser pulses of Nd:YAG (wavelength: 355, 532 nm and 1,064 nm). Colloidal nanoparticles have been characterized by UV–Vis spectroscopy and transmission electron microscopy. The obtained radius for the nanoparticles prepared using 1,064 nm irradiation lies in the range 15–30 nm, with absorption peak at 572 nm. Luminescence properties of Tb³⁺ ions in the presence and absence of Cu-nanoparticles have been investigated using 355 nm excitation. An enhancement in luminescence of Tb³⁺ by local field effect causing increase in lifetime of ⁵D₄ level of Tb³⁺ ion has been observed. Frequency and temperature-dependent conductivity of Tb³⁺ doped PVA thin films with and without Cu-nanoparticles have been measured in the frequency range 20 Hz–1 MHz and in the temperature range 318–338 K (well below its melting temperature). Real part of the conductivity spectra has been explained in terms of power law. The electrical properties of the thin films show a decrease in dc conductivity on incorporation of the Cu-nanoparticles.     

Concentration dependent Eu3+ doped boro-tellurite glasses—Structural and optical investigations

Eu³⁺ doped boro-tellurite glasses with the chemical composition (40?x)B₂O₃+30TeO₂+15MgO+15K₂O+xEu₂O₃ (where x=0.01, 0.1, 1, 2 and 3 wt%) have been prepared by following the conventional melt quenching technique. Structural and optical behavior of the prepared Eu³⁺ doped boro-tellurite glasses were studied and compared with reported literature. The XRD pattern confirms the amorphous nature and the FTIR spectral studies explore the presence of BO stretching vibrations, O₃BOBO₃ bond bending vibrations along with the bending vibration of TeOTe linkages in the prepared glasses. Through the optical absorption spectra, bonding parameters ($\overline{\beta },\delta$) were calculated to identify the ionic/covalent nature of the glasses. Judd–Ofelt (JO) parameters have been calculated from the luminescence spectral measurements. The JO parameters (Ω_λ, λ=2, 4 and 6) were used to calculate the radiative properties like transition probability (A), stimulated emission cross-section (${\sigma }_P^E$), radiative lifetime (τ_rad), and branching ratios (β_R) for the ⁵D₀→⁷F_J (J=0, 1, 2, 3 and 4) emission transitions of the Eu³⁺ ions. The local site symmetry around the Eu³⁺ ions were calculated through the luminescence intensity ratio (R) of the ⁵D₀→⁷F₂ to ⁵D₀→⁷F₁ transitions. The experimental lifetime of the ⁵D₀ level in the Eu³⁺ doped boro-tellurite glasses has also been calculated and compared with similar Eu³⁺ glasses. The lifetime of the ⁵D₀ level is found to be less than the reported glasses and it may be due to the presence of OH^? groups in the prepared glasses. The Optical band gap (E_opt), band tailing parameter (B) and the Urbach energy (ΔE) values of the prepared glasses were calculated from the absorption spectral measurements and the results were discussed and reported.     

Effect of gamma irradiation on the structural,thermal and optical properties of Makrofol BL 2–4

Makrofol BL 2–4 is an extrusion film based on Makrolon polycarbonate. It comprises excellent die-cutting performance combined with high light transmission and moderate light scattering properties. It is a class of polymeric solid state nuclear track detectors which has many applications in various radiation detection fields. In the present work, Makrofol samples were irradiated using different gamma doses ranging from 10 to 350 kGy. The structural modifications in the gamma-irradiated Makrofol samples have been studied as a function of dose using different characterization techniques such as X-ray diffraction, intrinsic viscosity, Fourier transform infrared spectroscopy, thermogravimetric analysis, refractive index and color difference studies. The gamma irradiation in the dose range 20–200 kGy led to a more compact structure of Makrofol polymer, which resulted in an improvement in its thermal stability with an enhancement in its structural and optical properties.     

Synthesis, structural and conductivity characterization of alginic acid–Fe3O4 nanocomposite

Alginic acid–Fe₃O₄ nanocomposite is synthesized by the precipitation of Fe₃O₄ in the presence of alginic acid (AA). Structural, surface, morphological, thermal and electrical transport properties of the nanocomposite were performed by XRD, FT-IR, TEM-SEM, TGA and conductivity measurements respectively. FT-IR analysis revealed that Fe₃O₄ NPs are strongly capped with AA and TGA analysis showed that nanocomposite have 80% of Fe₃O₄ content. TEM analysis of Fe₃O₄ NPs show an average particle size of 9.5 nm, and upon nanocomposite formation with AA these particles are observed to form aggregates of ~150 nm. The frequency-dependency of the AC conductivity show electrode polarization effect. Analysis of electrical modulus and dielectric permittivity functions suggest that ionic and polymer segmental motions are strongly coupled. DC electrical conductivity is strongly temperature dependent, and is classified into three regions over a limited temperature range of up to 100 °C.     

Anisotropic optical properties of single-crystal GdBa2Cu3O7−δ

The optical spectrum of reduced-T _c GdBa₂Cu₃O_7– has been measured for polarizations parallel and perpendicular to theab plane. The sample was an oxygen-deficient single crystal with a large face containing thec axis. The polarized reflectance from this face was measured from 20–300 K in the spectral region from 30–3000 cm^–1, with 300 K data to 30000 cm^–1. Kramers-Kronig analysis was used to determine the spectral dependence of theab and thec components of the dielectric tensor. The optical properties are strongly anisotropic. Theab-plane response resembles that of other reduced-T _c materials whereas thec axis, in contrast, shows only the presence of several phonons. There is a complete absence of charge carrier response alongc aboveand belowT _c. This observation allows us to set an upper limit to the free-carrier spectral weight for transport perpendicular to the CuO₂ planes.Permanent address: Institute of Physics, CSAV, Prague, Czechoslovakia     

The broadband NIR emission properties of Bi doped La2O3–Al2O3–SiO2 glass

Bi₂O₃ doped 65SiO₂–20Al₂O₃–15La₂O₃ (in mole%) glasses were prepared by the traditional melting–quenching method. The spectroscopic properties and mechanism of NIR broadband emission in these glasses were investigated in this work. Three excitation wavelengths of 500, 700 and 800 nm were used to test emission spectra. The emission band under 500 nm excitation can be regarded as combination of emission bands under 700 and 800 nm excitation. 2.0 mole% is found to be the optimal Bi₂O₃ doping level in this glass. Under 500 nm excitation its emission peak, FWHM and lifetime of emission band are 1160 nm, 300 nm and 569 μs, respectively. The longest fluorescent lifetime reaches 620 μs under 700 nm excitation. The valence state of Bi in these glasses is suggested to be lower than +3 by X-ray photoelectron spectroscopy. With the help of energy matching, we infer that both Bi⁰ and Bi⁺ centers are responsible for the NIR fluorescence of Bi₂O₃ doped 65SiO₂–20Al₂O₃–15La₂O₃ glass.