Silver Germanium Research Articles

Structural, electronic properties and reflectivity of ScTGe (Ag, Cu) Compounds

We have investigated structural, electronic and optical properties of half-Heusler materials Scandium Silver Germanium (ScAgGe) and Scandium Copper Germanium (ScCuGe) compounds by using state of the art FPLAPW based on the DFT. Optimization procedure is used to obtain the structural properties of the compounds. The bands of these compounds ScTGe(T= Ag, Cu) cross the Fermi level so these compounds show semi-metallic nature. The density of states shows mixed s and d states in the bands. From the optical spectrum of compounds, it is observed that reflectivity of these compounds is very high.

Self‐Assembled Silver–Germanium Nanolayer Metamaterial with the Enhanced Nonlinear Response

AbstractPlasmonic metamaterials and metasurfaces are important for many linear and nonlinear photonic applications. Here, the possibility to control a nanostructured layer spontaneously formed near an interface of a thin silver film is shown, where the interplay between a grain boundary structure and surface segregation of germanium atoms leads to encapsulation of the grains and, as the result, formation of a composite metamaterial near the film surface. This Ag/Ge composite exhibits strong localized surface plasmon resonances at Ge‐encapsulated silver grains, leading to extraordinary second harmonic generation for both transverse magnetic and transverse electric polarized fundamental light with up to two orders of magnitude enhancement compared to thin Ag films without Ge atoms. Segregation phenomena open the possibility for fabrication of a new class of composite materials and gives additional degree of freedom in designing optical properties of nanostructured metamaterials.

Effective decolorizations and mineralizations of organic dyes over a silver germanium oxide photocatalyst under indoor-illumination irradiation

A silver germanium oxide, Ag 2GeO 3, was developed as a novel photocatalyst for degradation of organic dyes. The chemical composition of the sample was investigated via the SEM/EDX, ICP-AES, and TG-DTA techniques. The general activity of the material was characterized by testing the photodegradations of typical organic dyes, such as Methylene Blue (one of the heteropolyaromatic dyes), Rhodamine B (one of the xanthene dyes), Fuchsin Acid (one of the sulfonic dyes), and Orange II (one of the azoic dyes). All of these dyes were degraded more than 90% within 25 min under the visible-light irradiation of Xe lamp. Besides, with a commercial white fluorescent lamp as testing light source (light intensity, 61 μW/cm 2), the efficient decolorizations and mineralizations of the organic dyes were achieved over this material: 79% (90%) of the organic carbon in the Methylene Blue (Rhodamine B) solution was photooxidatized to inorganic carbon forms, when these dyes were totally decolorized. The high performance of this material is due to the photophysical properties of the wide-visible-range absorption and response, and the sufficient oxidative potential of the top of the valence band.

Percolation transition in Ag-doped chalcogenide glasses: comparison of classical percolation and dynamic structure models

Homogeneity and electrical characteristics of Ag 2S–As 2S 3 glasses with silver concentrations ranging between 0.012 and 9.8 at.% have been investigated. It was found that diluted vitreous alloys ( x=0.012–1.2 at.% Ag) appear to be homogeneous according to scanning electron microscopy studies. Their electrical conductivity increases by a factor of 40 with corresponding decrease of the activation energy from 0.88 eV to 0.78 eV. The conductivity isotherm in this concentration range exhibits a power law composition dependence ( σ( x)∝ x t ), which is characteristic of percolation in the critical region just above the percolation threshold. In contrast to classical geometric percolation, t is temperature-dependent ( t∝ T −1)⋅ The power-law exponent at room-temperature ( t 25=0.78(6)) is smaller by a factor of 2.5 than that for a Ag 2S–GeS–GeS 2 glassy system in the same Ag concentration range and indicates that the electrical conductivity occurs within the framework of 2D percolation contrary to silver germanium sulphide glasses. Modified geometrical percolation predicts this decrease in t, which is not explained by the dynamic structure model.

Formation and undercooling of droplets in the primary phase of Ag-Ge alloys

The formation of micro-sized droplets in the matrix of the primary phase of Ag–Ge alloys and their undercooling behaviour were investigated. Thermal cycling consisted in equilibration of hypoeutectic alloys near the eutectic temperature in the two-phase liquid–solid region followed by up-quenching of alloys at 30–50°C above the eutectic temperature and their subsequent slow cooling. A wide size range of droplets was generated in the matrix of the silver-rich phase by repeated thermal cycling of the alloy. During slow cooling, droplets of silver-rich liquid exhibited a maximum undercooling of 81°C below the eutectic temperature. Examination of the solidification structure of the undercooled alloys, by X-ray diffraction, polarized light microscopy and electron probe micro analysis techniques, indicated the presence of a metastable phase. The mechanism of formation of droplets and the nature of non-equilibrium solidification of the undercooled melt of silver–germanium alloys, are discussed.

Crystallization of Amorphous Germanium in a Silver Germanium Layered System

ABSTRACTWe studied crystallization of amorphous germanium (a-Ge) induced in a Ag/a-Ge layered system, using in situ transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). Amorphous Ge was found to crystallize at about 270°C with the heat of reaction of 10±lkJ/mol. In situ TEM revealed that Ag grains migrate into the a-Ge phase leaving the crystalline Ge (c-Ge) phase behind. From this observation, we propose a model whereby the Ag provides the fastest path for the Ge atoms to diffuse from a-Ge to c-Ge phases.

Determination of germanium(IV) in perchloric acid solution by a.c. polarography and differential pulse polarography in the presence of 3,4-dihydroxybenzaldehyde

Germanium(IV) at trace levels can be determined in perchloric acid solution containing 3,4-dihydroxybenzaldehyde by alternating current and differential pulse polarography with dropping mercury and hanging mercury drop electrodes. The results are comparable by the two methods. The possible interferences of some elements are discussed. The serious interference of lead(II) can be prevented by addition of EDTA in hydrochloric acid medium. Interference of selenium can be avoided by precipitation with potassium iodide. The method is applied to silver—germanium alloys.

An x-ray diffraction study of lattice imperfections in cold-worked fcc alloys. III. Silver germanium (α phase)

Detailed x-ray Fourier line profile analysis has been performed on five compositions of cold-worked α-phase Ag-Ge alloys containing 1.48, 3.06, 4.51, 5.89, and 7.53 at.% of solute germanium. X-ray diffraction profiles from 111, 200, 220, 311, 222, and 400 reflections have been recorded in a Geiger-counter diffractometer with nickel-filtered copper radiation, and microstructural parameters have been evaluated from the line-shift, line-asymmetry, and line-shape analyses in an identical manner as done earlier in Papers I and II with Ag-Ga and Cu-Ga alloys, respectively. Quantitative estimations of intrinsic (α′), extrinsic (α″), and twin (β) stacking-fault probabilities have been made, and these have shown an increased presence of an intrinsic fault over the extrinsic fault and a total absence of deformation twin faults. The values of the dislocation density ρ have been evaluated, and from the parameter γ/μ (γ: stacking fault energy; μ: shear modulus), the stacking-fault energy of pure silver γ0 has been estimated (∼16–21 mJ/m2), which is found to be well within the general range of fault energy values observed for silver.

Formation of faulted close-packed structures in silver-germanium alloys quenched from the Melt

Abstract A series of silver—germanium alloys containing up to 25 at. % Ge was rapidly cooled from the liquid state by the Duwez technique and subjected to x-ray examination. The Debye-Scherrer patterns of the liquid-quenched alloys provide the first experimental proof for the incidence of light to heavy faulting in f.c.c. and h.c.p. phases on solidification.

Self-diffusion in dilute binary solid solutions—III: Diffusion in silver germanium and silver thallium solutions

The results of measurements of the diffusivities of silver in silver-thallium solutions and of thallium and germanium in pure silver and their corresponding solutions are reported. These data, and published solute and solvent diffusion data for silver-lead and silver-copper solutions, are in good agreement with predictions based on a previously proposed model for diffusion in dilute solid solutions.