Zn Ga Alloys Research Articles

Effect of twist-channel angular pressing on precipitation in Al–Mg–Zn–Ga alloys

Effect of twist-channel angular pressing on precipitation in Al–Mg–Zn–Ga alloys

Mechanical and Corrosion Properties of Hot-Extruded Mg–Zn–Ga Alloys

Mechanical and Corrosion Properties of Hot-Extruded Mg–Zn–Ga Alloys

Near-room temperature synthesis of Zn<sup>2+</sup>-doped γ-Ga<sub>2</sub>O<sub>3</sub> nanoparticles via direct oxidation of Zn–Ga alloy by ultrasound

This study used ultrasound irradiation to fabricate Zn2+-doped γ-Ga2O3 nanoparticles (NPs) from Zn–Ga alloy at near-room temperature (60 °C). The Zn2+-doped γ-Ga2O3 NPs were obtained at 60 °C after two steps of ultrasound irradiation (miniaturization and oxidation of Zn–Ga alloy). The specific surface area of Zn2+-doped γ-Ga2O3 NPs with a zinc content of 4 at.% was 90.4 m2/g. The oxidation behavior of Zn–Ga liquid alloy significantly differed from that of liquid Ga. X-ray photoelectron spectroscopy spectrum and lattice constant of Zn2+-doped γ-Ga2O3 confirmed Zn2+-doping into the γ-Ga2O3 crystal structure. By annealing at 900 °C, the obtained Zn2+-doped γ-Ga2O3 did not transform to Zn2+-doped β-Ga2O3 but to the mixed phase of β-Ga2O3 and ZnGa2O4. The results indicate that Zn2+ cations, with larger ionic radii than Ga3+ cations, are more difficult to be introduced into the β-Ga2O3 crystal lattice. Thus, this ultrasound process can potentially synthesize various metal cations-doped γ-Ga2O3 NPs without using high temperatures and pressures.

Effects of Zn/Ga ratio on microstructure, mechanical, damping and thermal properties of Mg–Zn–Ga alloy solid solutions

Effects of Zn/Ga ratio on microstructure, mechanical, damping and thermal properties of Mg–Zn–Ga alloy solid solutions

Effect of Heat Treatment on the Mechanical and Corrosion Properties of Mg-Zn-Ga Biodegradable Mg Alloys.

Mg alloys have mechanical properties similar to those of human bones, and have been studied extensively because of their potential use in biodegradable medical implants. In this study, the influence of different heat treatment regimens on the microstructure and mechanical and corrosion properties of biodegradable Mg–Zn–Ga alloys was investigated, because Ga is effective in the treatment of disorders associated with accelerated bone loss. Solid–solution heat treatment (SSHT) enhanced the mechanical properties of these alloys, and a low corrosion rate in Hanks’ solution was achieved because of the decrease in the cathodic-phase content after SSHT. Thus, the Mg–4 wt.% Zn–4 wt.% Ga–0.5 wt.% Y alloy after 18 h of SSHT at 350 °C (ultimate tensile strength: 207 MPa; yield strength: 97 MPa; elongation at fracture: 7.5%; corrosion rate: 0.27 mm/year) was recommended for low-loaded orthopedic implants.

Effect of Ga on the Oxide Film Structure and Oxidation Resistance of Sn-Bi-Zn Alloys as Heat Transfer Fluids.

The effect of gallium on the oxide film structure and overall oxidation resistance of low melting point Sn–Bi–Zn alloys was investigated under air atmosphere using thermogravimetric analyses. The liquid alloys studied had a Ga content of 1–7 wt.%. The results showed that the growth rates of the surface scale formed on the Sn–Bi–Zn–Ga alloys conformed to the parabolic law. The oxidation resistance of Sn–Bi–Zn alloys was improved by Ga addition and the activation energies increased from 12.05 kJ∙mol−1 to 22.20 kJ∙mol−1. The structure and elemental distribution of the oxide film surface and cross-section were found to become more complicated and denser with Ga addition. Further, the results of X-ray photoelectron spectroscopy and X-ray diffraction show that Ga elements accumulate on the surface of the liquid metal to form oxides, which significantly slowed the oxidation of the surface of the liquid alloy.

High-temperature corrosion of Sn–Bi–Zn–Ga alloys as heat transfer fluid

The new heat transfer alloy is highly reactive at high temperatures, and the corrosion of the container material determines the service life of the heat transfer system. The high-temperature corrosion of Sn–Bi–Zn–Ga alloys as heat transfer fluid was investigated. The microstructure and elemental distribution were studied by field emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy (EDS). The thermal properties before and after corrosion were studied by differential scanning calorimetry (DSC). The results show that the corrosion kinetics of the studied materials follows the parabolic law and the thermal properties after corrosion are improved. Ga significantly improves the thermal conductivity. 316 stainless steel exhibits excellent corrosion resistance due to its high Cr and Ni contents. Corrosion mechanism analysis shows that the oxidation of Ga has a smaller Gibbs free energy, and an oxide forms at the corrosion interface to prevent dissolution corrosion and oxidative corrosion of the container material.

Microstructures and Thermal Properties of Sn–Bi–Zn–Ga Alloys as Heat Transfer and Heat Storage Materials

Low melting point alloy is a potential high-temperature heat transfer medium because of the high thermal conductivity, low solidus temperature and wide range of use temperature. Consequently, we investigated the possibility of using Sn–Bi–Zn–Ga alloys as heat storage and heat transfer material. Moreover, we investigated the microstructure and phase compositions by electron probe micro-analysis (EPMA) and X-ray diffusion (XRD). Results show that the new structures and phases are formed in the alloy matrix with Ga additions, which lead to the improvement of the thermal properties. An extensive thermophysical characterization of the Sn–Bi–Zn–Ga alloys has been performed by differential scanning calorimeter (DSC) analysis. The addition of Ga lowers the peak temperature and increases the heat capacity of the alloys. The thermal expansion of the test alloys increases with increasing temperature and the densities decreases with Ga additions. As the density, specific heat capacity and thermal diffusivity change with temperature and physical state, the thermal conductivity of the alloys first decreases and then increases. These results demonstrate the feasibility of using Sn–Bi–Zn–Ga alloys as the high-temperature heat transfer fluid.

First-principles Investigation on Diffusion Mechanism of Zinc in n-GaSb

According to previous investigations, Zn diffusion in GaSb is mediated by dissociative mechanism or kick out mechanism. However, little work has been carried out to explain why Zn diffusion is mediated by these two different diffusion mechanisms. This work concentrated on the effect of diffusion sources (pure Zn and ZnGa alloy) on the diffusion mechanism mediating Zn diffusion in n-GaSb. First-principles method was employed to calculate the formation energies and migration barriers for interstitial Zn in all possible charges states at two tetrahedral sites. It was found that diffusion sources can influence the site of interstitial Zn, resulting in different diffusion mechanisms. Interstitial Zn is stable at anion-surrounded tetrahedral site under pure Zn condition, while stable at cation-surrounded tetrahedral site under ZnGa alloy condition. The results of diffusion activation energies demonstrated that kick out mechanism plays a dominant role for Zn diffusion in n-GaSb under ZnGa condition, and that under pure Zn condition, dissociative mechanism plays a dominant role at the beginning of the diffusion process and then kick out mechanism becomes dominant.

Identification of the dissociative and kick-out diffusion mechanisms of Zn diffusion in GaAs by photoluminescence analysis

Abstract Most investigations on Zn diffusion in GaAs were processed using the Zn–As alloy sources to prevent the As atoms from escaping GaAs wafers, while we found that the Zn diffusion would change fundamentally if Zn–Ga alloy sources were used. The Ga atoms from the diffusion sources suppressed the formation of the high-concentration surface region in Zn profiles, thus converting a kink-and-tail profile into a box profile. The photoluminescence (PL) analysis was used to identify the diffusion mechanisms. The Ga vacancy defects were found in the surface region of the kink-and-tail profile, indicating that the dissociative mechanism dominated; the PL spectrum in the tail region of kink-and-tail profile and the main region of box profile showed the same signals, no Ga vacancy defects were found, thus the kick-out mechanism dominated.

A novel zinc diffusion process for the fabrication of high-performance GaSb thermophotovoltaic cells

This paper reports a novel zinc diffusion method for forming emitters in GaSb thermophotovoltaic cells. A closed quartz-tube diffusion system using Zn–Ga alloys as the diffusion source was designed to realize p-type doping in N-GaSb wafers. The surface diffusion region showing a high concentration of zinc was suppressed by this diffusion method, and the GaSb cells fabricated using this method showed good quantum efficiency in the near-infrared bands. Compared to that of the conventional pseudo-closed-box diffusion method, the controllability of the etch-back process after front-side metallization is significantly improved, and the cost of the cell fabrication is reduced because no protective gas is required during the diffusion process.

Electrochemical behaviour of Al–Zn–Ga and Al–In–Ga alloys in chloride media

The influence of Ga content on the electrochemical behaviour of Al–Zn–Ga and Al–In–Ga alloys in chloride acid and acetic acid media was studied. The presence of Ga in concentration greater than 2.5wt.% causes an open circuit potential (OCP) shifts of Al–Zn–Ga alloys in chloride solution towards more negative values (−1.38V(SCE)). The OCP for Al–In–Ga alloys in chloride solution varies between −1.62 and −1.73V(SCE). The anodic behaviour of these ternary alloys can be interpreted in terms of an amalgam mechanism.

Thermodynamic investigations of Sn–Zn–Ga liquid solutions

Activity of zinc in liquid Sn–Zn–Ga alloys has been measured by electrochemical technique based on molten salt electrolyte galvanic cell in the temperature range 723–823 K along three pseudo-binary lines of Zn x (Sn y Ga 1− y ) 1− x where y = 0.75, 0.50 and 0.25. The excess molar free energy, enthalpy and entropy have been computed by the Darken's treatment of the ternary solutions using published data of the relevant binary solutions and ternary system investigated. Slope–intercept method has been used to compute the partial molar quantities. The activities of tin and gallium are computed from the partial molar excess free energies of three components at 750 K. The activities of all the three components show positive deviation from the Raoult's law. Thermodynamic properties of Sn–Ga binary system have been predicted at 750 K from the ternary data and compared with those published in the literature.

Polarisation behaviour of Al–Zn–Ga alloy in chloride medium

The electrochemical response of Al–Zn–Ga alloy in chloride medium was studied. For this purpose, linear sweep voltammetry and open circuit potential (OCP) measurements were employed and surface characterisation was performed by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis. The presence of Ga whether as alloyed element in the ternary alloy or deposited from the electrolyte solution onto pure Al or onto Al–Zn alloy causes a displacement of the onset of the process of dissolution towards more negative potential in a chloride solution. The anodic behaviour of the Al–Zn–Ga alloy can be interpreted in terms of an amalgam mechanism, where the homogeneously distribution of Ga in the alloy assures the formation of a superficial Ga–Al amalgam.

Structural, electrical, and optical properties of transparent conductive ZnO:Ga films prepared by DC reactive magnetron sputtering

Transparent conductive Ga-doped zinc oxide (ZnO:Ga) films with highly (0 0 2)-preferred orientation were deposited on glass substrates by DC reactive magnetron sputtering. Variation of structural, electrical, and optical properties with Ga content was investigated. The peak position of the (0 0 2) plane is linearly shifted to the lower 2 θ value with the increase of Ga content. The lowest resistivity of the ZnO:Ga films is 3.51×10 −4 Ω cm and the average transmittance of the films is over 90% in the visible range. The optical band gap of the films is in the range of 3.58–3.74 eV. The optimum growth condition was obtained by using the Zn–Ga alloy target of 3.0 at% Ga content.

The de Haas-van Alphen Effect and Anisotropy of the Magnetic Susceptibility in Zn–Ag and Zn–Ga Dilute Alloys

We report the results of measurements of the de Haas-van Alphen effect and the anisotropy of the magnetic susceptibility associated with the needle Fermi surface in the 3rd-band of pure zinc, dilute Zn–Ag and Zn–Ga alloys. The cross-sectional area of the needles increases for silver impurity, and decreases for gallium impurity. A large maximum in the temperature dependence of the anisotropy of the magnetic susceptibility is observed in pure zinc, Zn–Ag and Zn–Ga alloys. The temperature indicating its maximum increases in Zn–Ag and decreases in Zn–Ga alloys. These results of the magnetic susceptibility and the changes in the cross-sectional area of the needles with alloying can be reasonably accounted by temperature and impurity dependence of axial ratios.

Photoluminescence in ZnSe grown by liquid-phase epitaxy from Zn-Ga solution

Photoluminescence has been studied of epitaxial ZnSe layers grown from a pure Zn or a Zn-Ga alloy solution on ZnSxSe1−x (0⩽x⩽1) single-crystalline substrates. Intense blue emission bands at room temperature have been observed in the layers grown from a Zn-Ga alloy solution. The spectrum of the layer at 4.2 K generally consists of a strong emission line due to radiative recombination of excitons bound to the neutral donor, I2, an associated donor-acceptor pair emission band with LO-phonon replicas, and a deep-level emission, i.e., the so-called SA emission band. The effect of Ga on the emission spectrum is to greatly increase the intensity of the blue part of the spectrum. On the basis of the comparison between the experimental results and theoretical calculations, it is tentatively proposed that the blue emisison bands at room temperature originate from the radiative recombination due to band-to-band transition.

Liquid-phase epitaxy of ZnSe from Zn-Ga solution

Undoped or Ga doped ZnSe single crystal layers with thicknesses between 3 and 13 μm were grown on ZnS x Se 1− x (0 ⩽ x ⩽ 1) single crystal substrates by liquid phase epitaxy in a sealed tube system from a Zn or Zn-Ga alloy solution. Smooth and uniform epitaxial layers with high crystal perfection were obtained on the (111)- and (100)-oriented substrates. All the epitaxial layers were n-type and highly conductive (0.1 < ϱ < 10 Ω cm). A remarkable enhancement of the blue part of the photoluminescence spectra at room temperature was observed for the epitaxial layers grown from the Zn-Ga alloy solution.

New metastable electron phases in binary B-metal alloys

Utilizing the splat cooling technique of rapid quenching, nineteen binary B-metal alloy systems were investigated. The following non-equilibrium effects were observed at—190°C; new f.c.c. α phases in the Ag-In, Zn-Ga, and Cd-Sn systems; an extended f.c.c. α phase in Cd-In alloys in the composition range of 20 to 90% In; a new phase with an unknown structure in gallium-rich Zn-Ga alloys; a new simple hexagonal γ phase in Cd-Bi alloys; new phases in binary alloys of Ga with Cu, Ni, and Bi; and shifts in the equilibrium phase boundaries in the In-Sn system. All these non-equilibrium effects disappeared on heating to 20°C. The structural parameters of these phases were determined. The structures of the new metastable phases are determined primarily by the average valence electron concentration (VEC). The f.c.c. phases occur in a VEC range of 2.25–2.45 e/a; simple hexagonal γ phases occur in a VEC range of 3.4–3.9. Factors governing the formation of these phases are discussed.

Quantum efficiency of GaAs electroluminescent diodes

The external quantum efficiency of tin-doped GaAs diodes in the 10 16 to 5 × 10 18 cm −3 carrier concentration range was investigated. A maximum efficiency of about 0·18 per cent at 100° K was found at 5 × 10 17 cm −3 carriers, when a fixed diode geometry and ZnAs 2 junction diffusion at 870° C was employed. The results from a study of the effect of zinc diffusion conditions on efficiency indicate that a substantial increase in efficiency can be obtained by proper control of the zinc concentration gradient near the p− n junction. With the same fixed diode geometry, a quantum efficiency of 0·65 per cent (300° K) was obtained in tin-doped GaAs with a 1·7 × 10 18 cm −3 carrier concentration by employing a Zn-Ga alloy diffusion procedure to decrease the surface zinc concentration to less than 10 19 cm −3. Capacitance-voltage measurements indicate that this increased efficiency is associated with a linearly graded junction.