Cluster formation in Ag2O-P2O5-CdCl2 glass system

Ag₂O-P₂O₅ and Ag₂O-P₂O₅-20 wt% CdCl₂ glasses were prepared by melt quenching method and characterized with the help of several experimental techniques. Powder X-ray diffraction study indicated that the glasses are amorphous in nature. DSC studies showed that CdCl₂ doped glass is chemically more durable. Electrical conductivity and ionic transference number measurements have shown that both the glasses are ionic conductors with Ag⁺ ions as the charge carriers. The electrical conductivity of the doped glass is found to be higher than the undoped one. Structures of the glasses have been proposed on the basis of IR spectral analysis. From SEM studies it has been inferred that addition of 20 wt% CdCl₂ modifies the morphology of Ag₂O-P₂O₅ glass and in its presence formation of clusters composed of nanofibers occur.     

Evaluation of judd-ofelt intensity parameters for sm3+ and Dy3+ in a laser liquid

From the reported absorption measurements the spectral intensities of the observed bands of Sm³⁺ and Dy³⁺ ions in a SeOCl₂ + SnCl₄ laser liquid are reported in this paper. The judd-Ofelt intensity (T₂,T₄,T₆) parameters have been evaluated by a least-squares fit method. From the magnitude of the bonding parameter (δ), it is suggested that the Sm³⁺ and Dy³⁺ ions in the laser liquid studied may be found to be covalent in nature. By applying the Judd-Ofelt theory, a good correlation has been established between the experimental and calculated spectral intensities of the ions studied.     

Synthesis of ZnO/Zn2SiO4/SiO2 composite pigments with enhanced reflectance and radiation-stability under low-energy proton irradiation

ZnO/Zn₂SiO₄/SiO₂ composite pigments with nano-sized α-Zn₂SiO₄ interface phase were synthesized by a simple solid-state reaction method. It was found that the composite pigments exhibit significant improvement on the spectral reflectance and the proton radiation-stability compared with the pure ZnO pigment. The investigations have demonstrated that the enhancements on the spectral reflectance and the radiation-stability are attributed to the introduction of willemite Zn₂SiO₄ interface phase on the surface of ZnO matrix particles. In addition, the enhancement mechanisms of radiation-stability for ZnO/Zn₂SiO₄/SiO₂ composite pigments were discussed.     

Optical spectroscopy of single Cd0.6Zn0.4Te/ZnTe quantum dots on Si substrate

Microphotoluminescence (μ-PL) measurements were carried out to investigate the optical properties of single Cd_0.6Zn_0.4Te/ZnTe quantum dots (QDs) grown on Si (001) substrate by using molecular beam epitaxy. The high quality of single Cd_0.6Zn_0.4Te/ZnTe QDs is witnessed by resolution-limited emission, negligible background and absence of measurable spectral jitter or blinking. Polarization-dependent and power-dependent μ-PL spectroscopy measurements were performed to identify the exciton, the biexciton, and the charged exciton in the emission spectra of single QDs. Furthermore a weak linearly polarized line is observed on the low energy side of the neutral exciton and is ascribed to dark exciton recombination.     

Magnetisation of bulk Mn11Si19 and Mn4Si7

The purpose of this paper is to determine by experiment whether Mn₁₁Si₁₉ and Mn₄Si₇ in their bulk states have a finite magnetic moment or not. Magnetisation measurements were carried out on these materials using both SQUID system and Kerr rotation system. The high quality samples were grown using the temperature gradient solution growth method. SQUID measurements revealed that Mn₁₁Si₁₉ has finite magnetism while Mn₄Si₇ does not in their bulk states. It was also confirmed that Mn₄Si₇ became magnetic and Mn₁₁Si₁₉ got to exhibit a distinctive hysteresis in their powdery state. The enhancement of magnetism implied that the surface of the samples was to a great extent linked to its magnetism.     

Spectroscopic ellipsometry study of Cu2ZnGeSe4 and Cu2ZnSiSe4 poly-crystals

We report the room temperature spectroscopic ellipsometry study of Cu₂ZnGeSe₄ and Cu₂ZnSiSe₄ crystals, grown by modified Bridgman technique. Optical measurements were performed in the range 1.2–4.6 eV. The spectral dependence of the complex pseudodielectric functions as well as pseudo- complex refractive index, extinction coefficient, absorption coefficient, and normal-incidence reflectivity of Cu₂ZnGeSe₄ and Cu₂ZnSiSe₄ crystals were derived. The observed structures in the optical spectra were analyzed by Adachi's model and attributed to the band edge transitions and higher lying interband transitions. The parameters such as strength, threshold energy, and broadening, corresponding to the E₀, E_1A and E_1B interband transitions, have been determined using the simulated annealing algorithm.     

Optical properties of Tm3+-doped TeO2-WO3 glasses

Tm³⁺-doped TeO₂-WO₃ glasses have been prepared and their absorption spectra have been measured in the visible to IR (up to 7 μm) spectral region. Luminescence measurements have shown that the glasses have emission bands at 1.45 and 1.8 μm. An attempt was made to remove OH groups from the glasses using KBF₄ and an inert atmosphere during the glass preparation. The results demonstrate that a low OH content can be achieved only by combining these approaches. The 1.8-μm emission intensity in “dry” glass is a factor of 6 higher than that in the OH-containing glasses. The relevant Judd-Ofelt parameters have been calculated.     

Photo-electronic properties of InAs0.07Sb0.93 films

The temperature dependent photoconductive and surface barrier photovoltaic spectral responses of InAs_0.07Sb_0.93 films with an impurity density ～5.5×10¹⁵ cm^-3, grown by liquid phase microzone crystallization, are shown to be a function of their fundamental energy bandgaps shifted to values lower than those of InSb. From charge carrier transport measurements their absolute zero bandgap is calculated as ε_g0=0.197 eV, in good agreement with theory. In contrast with previously reported data on InAs_xSb_1-x solid solution bulk and single crystal layers, the electron mobility of InAs_0.07Sb_0.93 films increases with decreasing temperature reaching a value of ～1.32×10⁵ cm²/Vs at 77 K.     

Synthesis, characterization and photocatalytic properties of nanosized Bi2WO6, PbWO4 and ZnWO4 catalysts

Nanosized Bi₂WO₆, PbWO₄ and ZnWO₄ photocatalysts were synthesized by a mild hydrothermal crystallization process. The physical and photophysical properties of the catalysts were characterized by X-ray diffractometry, Brunauer-Emmet-Teller surface area and porosity measurements, transmission electron microscopy, Raman spectra, and diffused reflectance spectroscopy. The rhodamine-B photodegradation in aqueous medium was employed as a probe reaction to test the photoactivities of the as-prepared samples under four irradiation wavelengths. Bi₂WO₆ not only presented the photocatalytic activity in the wide spectral scope, including UV and visible light but also exhibited the strong photosensitized capability to transform RhB under visible light irradiation (λ > 490 nm). ZnWO₄ only displayed relatively high photoactivity under UV irradiation. However, PbWO₄ showed poor photoactivity under any light irradiation. On the basis of the calculated density functional theory (DFT), the photocatalytic mechanisms were discussed.     

Optimization of the thickness of glass/TiO2/Ag/Ti/TiO2/SiON multilayer film

The TiO₂/Ag/Ti/TiO₂/SiON multilayer film was deposited on glass substrate at room temperature using magnetron sputtering method. By varying the thickness of each layer, the optical property was optimized to achieve good selective spectral filtering performance in Vis-NIR region. The multilayer film achieves maximum transmittance of 92.7% at 690 nm, in which the both TiO₂ layers are 33 nm. For good conductivity and transmittance, a 4 nm Ti layer and a 30 nm SiON layer are necessary.     

New approach for generating Cu2O/TiO2 composite films for solar cell applications

In this paper, Cu₂O was studied as a photon absorber for solar cell applications. Cu₂O was deposited on a TiO₂ film using the electrochemical deposition (ECD) method. Based on the physical appearance of the samples, the particles of Cu₂O seemed to penetrate the TiO₂ film and were primarily deposited near the TiO₂/substrate interface rather than on the TiO₂ film surface. This method could be one way to generate a p-n bulk-heterojunction interface. The film was confirmed to be a Cu₂O/TiO₂ composite via X-ray diffraction measurements. The top electrode was formed by evaporating indium for I-V characterization, and the fabricated cell showed photovoltaic properties.     

Phase equilibrium of the VSe2/1bV3Se4 system and the thermodynamic quantities of the V3Se4 phase

The equilibrium selenium vapour pressure of V_xSe₂ (1.2 < x < 1.7) was measured by a thermobalance method at 1053, 1113 and 1163K under controlled selenium vapour pressure. The thermodynamic partial molar quantities of the V₃Se₄ phase were evaluated from the measured P_Se- X isotherms. Further, the powder X-ray and high temperature DTA measurements of the quenched specimens were carried out in order to identify the phase.     

Preparation and electronic properties of ceramic (V1−xCrx)2O3

Compacts of ceramic (V_1?xCr_x)₂O₃ for 0.006 ? x ? 0.013 were made by sintering material prepared by a co-precipitation method. Low temperature resistivity measurements were in general agreement with the single crystal results of McWhan and Remeika (1), but the paramagnetic insulator to metal transition was not sharp. High pressure Hall measurements through the ‘Mott’ transition have been measured for the first time. The Hall constant remained the same in sign and magnitude on both sides of the transition.     

Novel blue-emitting phosphor NaMg4(PO4)3:Eu, Ce with energy transfer

A blue-emitting phosphor of NaMg₄(PO₄)₃:Eu²⁺, Ce³⁺ was prepared by a combustion-assisted synthesis method. The phase formation was confirmed by X-ray powder diffraction measurement. Photoluminescence excitation spectrum measurements show that the phosphor can be excited by near UV light from 230 to 400 nm and presents a dominant luminescence band centered at 424 nm due to the 4f⁶5d¹ → 4f⁷ transition of Eu²⁺ ions at room temperature. Effective energy transfer occurs in Ce³⁺/Eu²⁺ co-doped NaMg₄(PO₄)₃ due to large spectral overlap between the emission of Ce³⁺ and excitation of Eu²⁺. Co-doping of Ce³⁺ enhances the emission intensity of Eu²⁺ greatly by transferring its excitation energy to Eu²⁺, and Ce³⁺ plays a role as a sensitizer. Ce³⁺-Eu²⁺ co-doped NaMg₄(PO₄)₃ powders can possibly be applied as blue phosphors in the fields of lighting and display.     

Annealing dependence of optical properties of Ga20S75Sb5 and Ga20S40Sb40 thin films

Amorphous Ga₂₀S₇₅Sb₅ and Ga₂₀S₄₀Sb₄₀ thin films were prepared onto glass substrates by using thermal evaporation method. The effect of annealing (under vacuum) at different temperatures on the optical parameters was investigated in the temperature range 373-593 K. The optical absorption coefficient (α) for the as-deposited and annealed films were calculated from the reflectance and transmittance measurements in the range 190-900 nm. X-Ray diffraction indicates that the as-deposited films and those annealed up to the glass transition temperature (T_g) exhibit amorphous state. On annealing above the glass transition temperature these films show a polycrystalline structure. Analysis of the optical absorption data indicates that the optical band gap E_g^opt of these films obeys Tauc's relation for the allowed non-direct transition. It was found that the optical band gap E_g^opt increases with annealing temperature up to T_g, whereas above T_g there is a remarkable decrease. The obtained results were interpreted on the basis of amorphous- crystalline transformation.     

Ammonia gas sensor based on PPy/ZnSnO3 nanocomposites

In this paper, Zinc stannate (ZnSnO₃) nanoparticles were synthesized by a sol-gel method. Then, polypyrrole (PPy)/ZnSnO₃ nanocomposites were prepared by a simple in situ chemical polymerization method. By means of X-ray diffraction, Fourier transform infrared and scanning electron microscopy, the microstructure of PPy/ZnSnO₃ nanocomposites was characterized. The XRD patterns indicate that ZnSnO₃ nanoparticles have a perovskite phase with an orthorhombic structure, and incorporation of PPy did not change the crystalline structure of ZnSnO₃. The PPy was evenly dispersed on the surface of ZnSnO₃ particles, which was endorsed by FTIR spectral analyses. SEM images indicate that the PPy was evenly dispersed on the surface of ZnSnO₃ particles without apparent agglomeration. We found that the nanocomposites exhibited a higher response to NH₃ gas.     

Electronic characterization of alkali ruthenium hollandites: KRu4O8, RbRu4O8 and Cs0.8Li0.2Ru4O8

Transport, specific heat, and magnetic measurements have been performed on three alkali hollandites: KRu₄O₈, RbRu₄O₈, and a newly synthesized Cs analog, Cs_0.8Li_0.2Ru₄O₈, which was determined to have space group I4/m (#87) and lattice parameters, a = 10.0850(4) and c = 3.12180(20). In contrast to the ruthenium perovskites, which display a wide range of electrical and magnetic behavior, the alkali hollandites are simple paramagnetic metals.     

Synthesis and characterization of europium(II)-holoborates,Eu2B5O9Cl and Eu2B5O9Br

Europium(II)-haloborates, Eu₂B₅O₉Cl and Eu₂B₅O₉Br, were synthesized and characterized by X-ray analysis, magnetic susceptibility and luminescent spectral measurements. The chloroborate Eu₂B₅O₉Cl crystallizes in the tetragonal system, D⁶₄-P4₂2₁2, with cell dimensions: a=11.349(4), $\text{c}\text{=6.500(4)}\text{A}\text{?}$ and Z=4, and Eu₂B₅O₉Br in the orthorhombic system, C¹⁰_2v-Pnn2 or D¹²_2h-Pnnm, with cell dimensions: a=11.503(3), b=11.382(3), $\text{c}\text{=6.484(2)}\text{A}\text{?}$ and Z=4. Both of them were paramagnets with paramagnetic Curie temperature at about ?1 K, and band emissions peaking at about 430 and 435 nm which were based on a 4f⁷-4f⁶5d transition of Eu²⁺ ion were observed on Eu₂B₅O₉Cl and Eu₂B₅O₉Br, respectively.     

Synthesis of single-phase Sr3Co2Fe24O41 Z-type ferrite by polymerizable complex method

Synthesis of single-phase Sr₃Co₂Fe₂₄O₄₁ Z-type (Sr₃Co₂Z) ferrite was realized by adopting the polymerizable complex method. Crystal structure of samples has been investigated by powder X-ray diffraction (XRD). Single-phase Sr₃Co₂Z ferrite was obtained by heating at 1473 K for 5 h in air. Magnetic properties were discussed by measurements of M-H curves with vibrating sample magnetometer (VSM). Sr₃Co₂Z ferrite prepared by polymerizable complex method showed typical M-H curve of soft ferrite, with a saturation magnetization of 21.5μ_B/formula unit (50.5 emu/g) and a coercive force of 0.014 T at room temperature.     

Effect of composition and deposition parameters on optical properties of Ge25Sb15−xBixS60 thin films

The optical constants of the Ge₂₅Sb_15−xBi_xS₆₀ (0?x?15) chalcogenide films, either as-deposited or after being annealed at various temperatures have been computed in the spectral wavelength range 400-2400 nm from the transmittance and reflectance measurements of normally-incident light. With the increase in bismuth content, the optical energy gap (which is indirect) decreases, while the refractive index increases. The effects of film thickness, substrate type, deposition rate and γ-radiation on optical properties have been studied. The effect of thermal annealing on the growth characteristics and stability of the films has been studied using X-ray diffraction and scanning electron microscopy. The dispersion of the refractive index is discussed in terms of the single-oscillator Wemple-DiDomenico model.