Structure and optical properties of CuxO- and CuxSe-doped sol–gel silica glasses

Copper oxide and copper selenide nanoparticles were produced within the silica glasses through the sol–gel technique. Chemistry of these copper compounds (variability in stoichiometry and copper oxidation state) provides a variety of optical properties of nanoparticles composed from them. A series of glasses with the nanoparticles different in stoichiometry was fabricated. The linear absorption spectra reveal the changes of the fundamental absorption edge position and appearance of the intense absorption band in the near IR. Photoluminescence is observed both for copper oxide and copper selenide nanoparticles evidencing Cu(I) states.     

Structural characterizations and optical properties of new Li–Sr–Nb-phosphate glasses

A new Li₂O–SrO–Nb₂O₅–P₂O₅ glass system was prepared by a high-temperature alumina crucible, and structural characterization and optical properties were investigated. Proper content of Li₂O and Nb₂O₅ was employed to replace partial SrO and P₂O₅ to improve the optical properties. It was observed that the enhancement of the refractive index from 1.75 to 1.85 is mainly due to the Nb₂O₅ content. An addition of Li₂O significantly increases the optical transmittance; optical transparency can be enhanced from 60% to higher than 85% in the UV–visible region with addition of 20–40 mol% Li₂O species. However, optical transmittance is monotonically decreased from about 90% to 80% under 10–30 mol% Nb₂O₅ addition. The 40P₂O₅–20Nb₂O₅–20SrO–20Li₂O glasses demonstrate the optimum refractive index (n > 1.75) and high optical transparency (>80%) in the UV–visible region.     

Optical absorption and photoluminescence properties of Eu3+-doped ZnF2–PbO–TeO2 glasses

Several physical, optical absorption and photoluminescence properties of Eu3+-doped ZnF2–PbO–TeO2 glasses have been studied. From the measured intensities of various absorption bands of these glasses the Judd–Ofelt parameters 2, 4 and 6 have been computed. The Judd–Ofelt theory has been applied to characterize the photoluminescence spectra of these glasses. From this theory, various radiative properties, such as transition probability, A, branching ratio, r, and emission cross-section, EP, for various emission levels of these glasses, have been determined and reported. © 1998 Chapman & Hall.     

Structural investigations of some bismuth–borate–vanadate glasses doped with gadolinium ions

X-ray diffraction (XRD), Fourier transform infrared (FTIR) and electron paramagnetic resonance (EPR) spectroscopies have been employed to investigate the xGd₂O₃ · (95 − x)[2Bi₂O₃ · B₂O₃] · 5V₂O₅ glass system, with 0 ≤ x ≤ 25 mol%. The glass samples have been prepared by melting at 1,100 °C for 10 min followed by rapid cooling at room temperature. The structure of samples was analyzed by means of XRD. The pattern obtained did not reveal any crystalline phase in the samples up to 25 mol%. FTIR spectroscopy data suggest that the gadolinium ions play the network modifier role in the studied glasses. These data show that the glass network consists of BiO₃, BiO₆, BO₃, BO₄, and VO₄ structural units. The FTIR data show that a conversion among these units takes place and this process mainly depends on the Gd₂O₃ content. The EPR spectra of the studied glasses exhibit three important features with effective g-values of ≈5.9, 2.85, 2.0 and a weaker feature at g _eff ≈ 4.8. For low Gd₂O₃ contents (x ≤ 10 mol%), the EPR spectra have the typical ‘‘U’’-type shape. For higher contents of Gd₂O₃ (x > 10 mol%), the spectral features are broadened and finally are dominated by a single broad absorption line located at g _eff ≈ 2.0. This broad EPR line is associated to the Gd³⁺ ions present predominantly as clustered species.     

Linear and nonlinear optical properties and luminescence of Dy+3-doped aluminoborate glasses: Judd–Ofelt investigation

The nominal glasses composition ((40-x) % H₃BO₃—30% CaO—30% Al₂O₃—x Dy₂O₃), where x?=?1, 2, 3, 4, 5 and 6) were prepared using the melt quenching technique. The absorption spectra reveal the common normal 13 transition peaks of the Dy₂O₃-doped glasses. The linear and nonlinear optical properties were calculated. The Photoluminescence spectra and the decay lifetime were examined. The Judd–Ofelt parameters trend was Ω₄?>?Ω₂?>?Ω₆. The oscillator strength of the experimental, and calculated electronic dipole absorption transition were estimated. The radiative life-time, the radiative branching ratio, the emission and absorption transition cross section were also calculated. The gain coefficient of the transitions was predicted. All the calculated parameters were compared with the previous work. The results reveal that the current glasses composition is a good candidate as a lasing host material and the glasses are highly efficient composition when using in the optical communication fibers.

     

Development of biomimetic coatings on Sm oxide doped ELB (Eu–Li–borate) glasses

The in-vitro biomineralization of Eu/Li–borate glasses containing Sm₂O₃ was investigated by immersion in simulated body fluid (SBF) up to 72 h. Back scattering scanning electron microscope supplemented with EDX was used to follow the development of the phosphatic layer post 72 h SBF immersion. Biochemical analyses of calcium and inorganic phosphorus (Ca²⁺ and iP) ions were conducted using relevant biochemical kits and spectrophotometer. Spectra of TF-X-ray analyses and Fourier transform infrared were obtained for the samples post 72 h immersion and compared to the host one.The role of Sm₂O₃ in the biomineralization and crystallinity of the (ELB) borate glasses is proved by the developed rounded nano particles and the presence of elemental Eu and Sm in the formed layer beside Ca and P as presented by EDX. The continuous reduced values of ionic iP accompanying the adsorption and release of Ca ions in SBF with time assured the biolayer formation. The formed phosphatic layer presented shifted XRD peaks due to ionic incorporations especially of Sm³⁺. FT-IR proved the selectivity of BO₃ group for phosphatic deposition. Deconvolution of ν₄ and ν₃ regions, for carbonates and phosphates, respectively, proved the enhanced peak areas with increased Sm³⁺ content.     

Structural verification and optical characterization of SiO2–Au–Cu2O nanoparticles

In this paper, SiO₂–Au–Cu₂O core/shell/shell nanoparticles were synthesized by reducing gold chloride on 3-amino-propyl-triethoxysilane molecules attached silica nanoparticle cores for several stages. Cu₂O nanoparticles were synthesized readily with the size of 4–5 nm using a simple route of sol–gel method Then, they were clung to the surface of Au seeds. The morphology of the resultant particles was studied using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Transmission electron microscopy images demonstrate growth of monodispersed gold seeds and Cu₂O nanoparticles in narrow size up to 10 nm and 5 nm, respectively. The presence of gold and Cu₂O coating was confirmed by X-ray diffraction, Fourier transform infrared spectroscopy and UV–Vis spectroscopy. Absorption spectroscopy shows considerably 40 nm blue shift in absorption edge for SiO₂–Au–Cu₂O nanostructure rather than SiO₂–Au core/shell nanoparticles.     

Structural, vibrational, optical and magnetic properties of sol–gel derived Nd doped ZnO nanoparticles

Nd doped ZnO (Zn_1-xNd_xO, x = 0.0, 0.03, 0.06 and 0.10) nanoparticles were prepared by sol–gel method. Phase identification and effect of Nd ions substitution in ZnO lattice were confirmed by Rietveld analysis of XRD patterns. UV–Visible absorption spectra of pure and Nd doped ZnO nanoparticles showed the variation of the band gap in the range of 3.31–3.26 eV. The FTIR analysis of pure and Nd doped ZnO nanoparticles exhibited similar patterns in Zn/Nd–O bond length as obtained from the Rietveld refinement. Raman analysis confirmed the formation of a wurtzite structure wherein the local structure of ZnO nanoparticles is distorted due to Nd substitution. Magnetization-magnetic field hysteresis curves for pure and Nd doped ZnO nanoparticles revealed diamagnetic and paramagnetic behaviour, respectively. The paramagnetic behaviour of doped ZnO nanoparticles increased with increasing Nd concentration. However, the weak ferromagnetic behaviour of doped ZnO nanoparticles is observed after subtracting paramagnetic components, whereas the ferromagnetic behavior increased up to x = 0.06 samples, which further declined for x = 0.10 sample due to competition between paramagnetic and ferromagnetic ordering. The reduction in the ferromagnetic behavior for x = 0.10 sample indicates that the solubility limit of Nd atoms in ZnO lattice has been reached and paramagnetically coupled Nd atoms increased due to the increasing secondary phases.     

Structural and dielectric studies of Eu3+/Ag nanocrystallites: SiO2–TiO2 matrices

Silver nanocrystallites/Eu³⁺ doped SiO₂–TiO₂ matrices were synthesised through sol–gel route and the structural and dielectric properties of the matrices were studied. Structural characterizations were done using EDX, XRD, FTIR, AFM and TEM measurements. The TEM and XRD measurements confirm the presence of Ag and TiO₂ nanocrystals. The dielectric and electrical conductivity studies of the samples were done for a frequency range of 100 Hz–2 MHz. The conductivity variation with the Ag content in the Eu³⁺ doped SiO₂–TiO₂ system has been explained by correlating the presence of ionic contribution to the electrical conductivity process. Also, the frequency dependence of dielectric constant and conductivity were studied. The Cole–Cole parameters were calculated and the semicircles observed in the plots indicate a single relaxation process. This behaviour can be modelled by an equivalent parallel RC circuit.     

Preparation and optical properties of TPPS-doped metal–carboxylate-salts glasses

Li and Na carboxylate salts glasses with different number chains containing molecules of Tetraphenyl-porphine-tetrasulfonic acid (TPPS) were prepared by the melting method. TPPS doped in the glasses had the same form as the TPPS in the aqueous solutions. However the form of TPPS in the glasses changed because TPPS reacted with matrix glass during the melting process. Tetraphenyl-porphine (TPP) could no be incorporated into the Li and Na carboxylate salts glasses by the present melting method. The free base TPPS is important for photochemical hole burning (PHB) properties, and a mixed metal–carboxylate salts glasses containing free-base TPPS, which is the active form for PHB, were prepared by controlling the melting condition. It was found that a preparation condition such as holding time of the melts affects the formation of the complex of the TPPS and that in the mixed metal–carboxylate salts melts the TPPS formed a complex with Li but did not form a complex with Na.     

Preparation and optical properties of TPPS-doped metal–carboxylate-salts glasses

Li and Na carboxylate salts glasses with different number chains containing molecules of Tetraphenyl-porphine-tetrasulfonic acid (TPPS) were prepared by the melting method. TPPS doped in the glasses had the same form as the TPPS in the aqueous solutions. However the form of TPPS in the glasses changed because TPPS reacted with matrix glass during the melting process. Tetraphenyl-porphine (TPP) could no be incorporated into the Li and Na carboxylate salts glasses by the present melting method. The free base TPPS is important for photochemical hole burning (PHB) properties, and a mixed metal–carboxylate salts glasses containing free-base TPPS, which is the active form for PHB, were prepared by controlling the melting condition. It was found that a preparation condition such as holding time of the melts affects the formation of the complex of the TPPS and that in the mixed metal–carboxylate salts melts the TPPS formed a complex with Li but did not form a complex with Na.     

Structural,electrical, and magnetic properties of erbium (Er3+) substituted Cu–Cd nano-ferrites

In the present work, we reported the structural, electrical, and magnetic properties of erbium Er³⁺-substituted Cu–Cd nano-ferrites with generalized formula Cu_0.8Cd_0.2Er_xFe_2?xO₄ (where x?=?0.000, 0.0010, 0.0015, 0.002, 0.0025, 0.003), as synthesized by the Citrate-Gel Auto-Combustion. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) studies were carried out to investigate their microstructural and surface morphology. The XRD measurements confirm pure cubic spinel phase composition of these nanoparticles. The crystallite size ranges over 9.22–19.22 nm and it reduces with the increase in erbium Er³⁺ concentration from 0.000 to 0.003. The vibration properties were carried out by using FTIR spectrometer. The two probe measurements were used to determine DC resistivity, Curie temperature, and DC conductivity. The plot between DC electrical resistivity and temperature indicates the semiconductor behavior. At room temperature, the vibrating sample magnetometer (VSM) was used to investigate magnetic properties, and the observed values revealed the ferrimagnetic behavior with high saturation magnetization (34.24 emu/g) and high coercivity (1121.70 Oe).

     

Luminescence and energy transfer in Er3+/Nd3+ ion-codoped Ge–In–S–CsBr chalcohalide glasses

This study investigates the emission properties of the Er³⁺/Nd³⁺ ions codoped 70GeS₂–10In₂S₃–20CsBr chalcohalide glasses. The vacuumed melt-quenching technique is employed to synthesize the glasses. The absorption spectra, upconversion and near-IR emission spectra as well as fluorescence decay curves are collected. With the increasing concentration of Er³⁺ ions, the lifetimes at 1073 nm for Nd³⁺ ions decrease from 538 to 420 μs under 808 nm excitation. Meanwhile, the lifetimes at 1540 nm for Er³⁺ ions decrease from 245 to 214 μs with the increasing concentration of Nd³⁺ ions. The emission spectra and lifetimes show that energy transfer exists between the Nd³⁺ and Er³⁺ ions. The luminescence and detailed energy transfer mechanisms are schematically proposed.     

Structural and physical characterization of the Li2O∶P2O5∶CrO1.5 ion-conducting glasses

Li₂OP₂O₅CrO_1.5 glasses containing 40, 50 and 60 mol% Li₂O and a varying P₂O₅-to-CrO_1.5 ratio have been synthesized. The glass-transition temperature and density increase as P₂O₅ is progressively replaced by CrO_1.5. The glasses, being green in colour and showing strong optical absorption at 450 nm and 660 nm, contain predominantly Cr^{3 +} ions and a relatively small amount of Cr^{6 +} ions. The proportions of phosphate species with one, two, and three non-bridging oxygen atoms are determined from Raman spectroscopy results. From X-ray photoelectron spectroscopy (XPS) binding energies of the Li 1s, P 2p, Cr 2p and O 1s core levels are determined. The O 1s spectrum is found to consist of two peaks which are attributed to the P=O, P-O-P, P-O, P-O-Cr, and Cr-O oxygen species. Conductivity of these glasses increases with increasing Li₂O content and with progressive replacement of P₂O₅ by CrO_1.5. The 0.60Li₂O O.32P₂O₅0.08 CrO_1.5 glass is found to have the highest conductivity, 3.2×10^–6–1 cm^–1 at 25 °C. Compositional dependence of the conductivity is discussed in relation to variations in the glass structure.     

Enhancing the physical,optical and shielding properties for ternary Sb2O3–B2O3–K2O glasses

Ternary Sb₂O₃–B₂O₃–K₂O glass system, with general composition of x Sb₂O₃–(70-x) B₂O₃–30 K₂O (where x?=?0, 10, 20, 30, 40, 50) were prepared using melt-quenching technique. Structures of these glasses were investigated using XRD analysis and FT-IR spectroscopy. The optical properties were investigated using the UV–Vis NIR JASCO (Model V-670) Double Beam Spectrophotometer. Different physical parameters, such as density (ρ), molar volume (V_M), oxygen molar volume (V_O) and oxygen packing density values (OPD) have been estimated. Also, the Gamma radiation shielding ability have been characterized for the investigated glasses using Phy-X/PSD software in the photon energy range (0.015–15 MeV). XRD analysis confirm the amorphous nature of the prepared glasses. The optical energy gap of SBK glasses is decreasing from 4 to 2.63 eV with increasing Sb₂O₃ content while refractive index is increasing from 2.17 to 2.5 because of increasing the non-bridging oxygens (NBOs) in the glass matrix. The molar refractivity (R_m), molar polarizability (α_m) and the third-order nonlinear optical susceptibility values χ³ have been calculated, their values are found to increase with increasing Sb₂O₃ content. Glass density and molar volume values for the SBK glasses increase with increasing Sb₂O₃ content. Increasing the Sb₂O₃ concentration enhance the radiation shielding features of the prepared glasses against gamma rays and neutrons. Hence, the mass attenuation coefficient (MAC) increases from 8.6 to 35.4 cm²/gm while the half value layer (HVL) decreases from 0.036 to 0.0046 cm at 0.015 MeV as the Sb₂O₃ concentration increases from 0 to 50 mol%. The fast neutron cross section of the six investigated SBK glasses are (0.087, 0.092, 0.095, 0.091, 0.094 and 0.092 cm^?1), respectively.

     

AC electrical and optical characterization of epoxy–Al2O3 composites

The AC electrical and optical characterizations of epoxy–alumina (Al₂O₃) composites have been investigated. Sheets filled with alumina were prepared with different alumina concentrations (0, 2, 5, 8, 10, and 15 wt%). The AC electrical properties were measured by using impedance spectroscopy as a function of applied frequency in range from 50 kHz to 1 MHz and filler concentration. The results obtained showed that the applied frequency and filler concentration was found to influence the AC electrical conductivity and dielectric behavior of the prepared composites. The UV-optical results obtained were analyzed in terms of the absorption formula for non-crystalline materials. The absorption coefficient and the optical energy gap (E_opt) have been obtained from the direct allowed transitions in k-space at room temperature. The tail widths (ΔE) of the localized states in the band gap were evaluated using the Urbach-edges formula. It was found that both (E_opt) and (ΔE) vary with the alumina concentration dispersed in the epoxy matrix. The refractive index (n) for the composites was determined from the collected transmittance and reflectance spectra. The dispersion behavior of the refractive index is discussed in terms of the single oscillator model.     

Structural and physical properties of Ni–Tb–Fe–O system

A series of soft ferrites in the system Ni_1 ? xTb_xFe₂O₄ (0 ≤ x ≤ 0.2), was prepared by a standard ceramic technique. The influence of terbium content was investigated by means of X-ray diffraction, Fourier Transform Infrared (FTIR) spectroscopy and scanning electron microscopy. The X-ray diffraction analysis reveals that the samples have a cubic spinel (single phase) structure for 0 ≤ x ≤ 0.08; for x > 0.08 a small peak of orthorhombic phase (TbFeO₃) appears and becomes more conspicuous with increased terbium substitution. The lattice parameter changes in a non-linear way as a function of terbium content which may be attributed to differences in the ionic radii of the cations involved and the solubility limit of terbium ions. A gradual increase in the bulk density was observed with the increase of terbium concentration, from 5.13 g/cm³ to 5.69 g/cm³. FTIR absorption spectra of the Ni–Tb–Fe–O system were investigated in the wave number range 370–1500 cm^? 1. Each spectrum exhibited two main absorption bands, thereby confirming the spinel structure.     

Structural,dielectric, and reflection characterization of 0.96 ZnxMg1−xTiO3–0.04 SrTiO3 ceramics

Journal of Materials Science: Materials in Electronics - The impact of Zn substitution on structural, dielectric, and reflection properties of the pure MgTiO3 and 0.96 ZnxMg1?xTiO3–0.04...     

Effect of processing parameters on textural and bioactive properties of sol–gel-derived borate glasses

A compositional range of recently developed bioactive sol–gel-derived borate glasses (SGBGs) have demonstrated remarkably rapid rates of conversion to hydroxy-carbonated apatite (HCA) in simulated body fluid (SBF). Although the composition of SGBGs did not greatly impact HCA conversion rates, it is still unknown how the sol–gel processing parameters affect the textural properties and thus bioactivity of the glass. In this study, a borate-substituted Bioglass^® “45S5” formulation [(46.1)B₂O₃-(26.9)CaO-(24.4)Na₂O-(2.6)P₂O₅; mol%] was fabricated using different sol–gel processing parameters including precursor materials, ageing time and temperature, along with calcination rate and temperature. It was found that a higher calcination temperature led to a partially crystallized glass with almost a magnitude decrease in specific surface area relative to the other glasses. All processing routes resulted in highly bioactive glasses according to Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy, which confirmed HCA formation in SBF in as little as 2 h. The majority of ion-exchange occurred within 30 min, facilitating this rapid conversion to bone-like HCA. Interestingly, the partially crystallized glasses (i.e., glass–ceramics) also underwent full conversion to HCA in SBF. Furthermore, ageing time and temperature did not affect the bioactive properties of these glasses, which allow for significantly reduced processing times. In summary, this study demonstrates that SGBGs can be tailored for targeted tissue engineering applications by varying the sol–gel processing parameters.