Cd Alloy Research Articles

Role of Short-Range Order in Martensitic Transformation

Ohba, Otsuka and Sasaki [1] have established that the rubber-like behavior in the martensitic phase of Au-47.5at%Cd alloys cannot be caused by the change in the long-range order during the room temperature annealing. The rubber-like behavior should be understood in terms of the mechanical relaxation associated with the change in the orientation of the local short range order. It is proposed that, while the short-range order plays a prominent role in the rubber-like behavior in the martensite, it should play a comparably important role also in the austenite.

Chemistry and structure of CdO/Ag{222} heterophase interfaces.

The atomic scale structure and chemistry of the terminating polar plane of CdO, at atomically clean CdO/Ag{222} interfaces, produced by internal oxidation of a Ag(Cd) alloy, is studied via high-resolution electron (HREM) and atom-probe microscopies. It is demonstrated that this {222} plane can be either O or Cd with equal probability. The HREM and atom-probe results provide evidence for atomic-height steps at the CdO/Ag{222} interface. The results are explained in terms of precipitate coarsening during the internal oxidation process used to prepare the interfaces.

Radiological characterization of spent control rod assemblies

Abstract Three different spent control rods were obtained for direct-assay measurements and empirical sampling and analysis. They were: 1) a BWR cruciform control rod, 2) a PWR rod-cluster control assembly, and 3) a burnable poison-rod assembly. The dominant activity of the BWR cruciform control rod and the PWR burnable poison-rod assembly is60Co, whereas the PWR rod-cluster control assembly is dominated not only by60Co, but also by108mAg and110mAg, which are found in the Ag–In–Cd alloy of the absorber rods. The radionuclide inventories calculated for the three spent control rods from the empirical sampling data agree very well with data determined from the two direct assay methodologies. The concentration of108mAg in the rod-cluster control assembly will have to be considered when these types of spent control rods are prepared for waste disposal.

Infrared reflection spectra of CdIn2O4 films

The infrared (IR) reflection spectra of CdIn2O4 films produced by rf reactive sputtering from a Cd-In alloy target in a reactive Ar+O2 atmosphere have been investigated. Experimental results show that IR reflection spectra from CdIn2O4 films changed with increasing oxygen concentration and heat treatment, and the results obtained are discussed briefly.

ジルコニア固体電解質電池法による溶融Zn-In系，Cd-In系合金の活量測定

ジルコニア固体電解質電池法による溶融Zn-In系，Cd-In系合金の活量測定

Plastic Deformation of Polycrystalline Zn-0.25%Cd Alloy and Linear Location of Acoustic Emission

Plastic Deformation of Polycrystalline Zn-0.25%Cd Alloy and Linear Location of Acoustic Emission

Effect of ageing ζ' 2 martensite on the enthalpy of transformation in a Au-49.5 at% Cd alloy

The effect of martensite ageing in shape memory alloys is a serious problem in their applications. Although the origin for the effect is still controversial, one feasible origin is believed to be the reordering of martensites with ageing. If that is the case, the free energy or the enthalpy of transformation ( ΔH) is expected to change with ageing. To test such a possibility, DSC measurements were carried out for the reverse transformation of the ζ' 2 (trigonal) martensite in an Au-49.5 at% Cd alloy single crystal, and the change in ΔH with ageing was found for the first time.

The rubber-like behavior of ζ' 2 (trigonal) martensite in Au-49.5 to 50.0 at% Cd alloys

The effect of ageing ζ' 2 (trigonal) martensite in Au-49.5 to 50.5 at% Cd alloy single crystals was studied both by tensile tests and optical microscope observations. As a result, the rubber-like behavior associated with the ζ' 2 martensite was found for the first time. Furthermore, the yield stress in the martensitic state was found to increase with the square root of ageing time. Thus, the ageing effect and the appearance of the rubber-like behavior are shown to be closely related with diffusion via vacancy mechanism.

Melting behaviour of cadmium particles embedded in an aluminium matrix

An Al-4.5% Cd alloy has been manufactured by melt spinning to produce a microstructure of 14–150 nm diameter faceted cadmium particles embedded in an aluminium matrix. The melting behaviour of the cadmium particles has been investigated by differential scanning calorimetry. The melting point of 20 and 14 nm diameter cadmium particles embedded are depressed by 7 and 9 K respectively, below the bulk equilibrium cadmium melting point, because of Gibbs-Thomson capillarity effects. The average solid cadmium particle/aluminium matrix interfacial energy is 27 mJ m−2 higher than the average liquid cadmium particle/aluminium matrix interfacial energy. No significant superheating is needed to nucleate cadmium particle melting.

Wide gap Cd 1−xMg xTe: molecular beam epitaxial growth and characterization

We have grown the ternary alloy Cd 1- x Mg x Te as well as Cd 1- x Mg x Te/CdTe quantum well structures by molecular beam epitaxy - to our knowledge for the first time. Cd 1- x Mg x Te exhibits some very interesting features: The band gap has been determined as a function of Mg concentration, and a band gap of 3.0 eV was found for zincblende MgTe at room temperature. Cd 1- x Mg x Te thin films with Mg concentrations of up to 0.75 were fabricated, which corresponds to a band gap of 2.8 eV at low temperatures. Therefore, the whole visible band gap range (at room temperature) can be covered with Mg concentrations between 0.30 (red) and 0.75 (blue). Bulk MgTe crystallizes in the wurtzite structure, but zincblende MgTe could be grown on (100) oriented CdTe substrates up to a layer thickness of approximately 500 nm. The lattice mismatch between zincblende MgTe and CdTe was found to be as small as 1.0%. The growth of cubic MgTe could be followed by reflection high energy electron diffraction (RHEED) oscillations. In general, excellent structural quality could be reached, which is demonstrated by the FWHM of 22 arc sec for a Cd 1- x Mg x Te thin film with 0.44 Mg concentration on a Cd 1- x Zn x Te nearly lattice matched substrate. The Poisson number of Cd 1- x Mg x Te has been determined by X-ray diffraction as a function of Mg concentration. Cd 1- x Mg x Te/CdTe single quantum well structures have been fabricated with a large confinement energy of up to 0.8 eV. The photoluminescence spectra show exciton lines with very narrow linewidths. We are able to observe excited exciton states, and from the energetic difference between 1s and 2s heavy hole exciton lines we deduce exciton binding energies. Very bright luminescence could be seen even at room temperature, which is an indication of a large exciton binding energy and an effective radiative recombination.

Liquefaction of Zircaloy-4 by molten (Ag, In, Cd) absorber alloy

The (Ag, In, Cd) alloy which is used in LWRs as absorber material melts at about 800°C. After mechanical and/or chemical failure of the stainless steel absorber rod cladding at elevated temperatures, the molten absorber alloy interacts chemically with the Zircaloy guide tube and Zircaloy cladding of the fuel rods and dissolves them. Stainless steel is not attacked by the (Ag, In, Cd) alloy. The knowledge of the reaction kinetics between the (Ag, In, Cd) alloy and Zircaloy is important for the description of core degradation phenomena and has therefore been investigated at temperatures up to 1200°C. The behavior at higher temperatures could not be studied because of the fast liquefaction of Zircaloy by the absorber alloy during heatup. It was found that thin oxide layers on the Zircaloy surface can delay the chemical interactions with the molten (Ag, In, Cd) alloy but they cannot prevent them, because the ZrO 2 layers possibly disappear under the formation of oxygen-stabilized α-Zr(O). These chemical interactions can be described by parabolic rate laws; the corresponding Arrhenius equations are given.

Conduction band edges charge densities in Cd xZn 1−xS

The empirical pseudopotential method coupled with the virtual crystal approximation is used to compute the electronic conduction band-edge charge densities at the Γ and X points for the ternary alloy Cd xZn 1−xS. We find that these charge densities are strongly dependent upon the stochiometric coefficient x. Such differences are crucial for a comprehensive understanding of interstitial impurities and the response of specific band states to perturbation in ternary alloy semiconductors.

Exciton dynamics in zinc-rich CdZnTe/ZnTe quantum wells

In this review we detail the dynamics of intrinsic excitons in the alloy Cd x Zn 1- x Te/ZnTe quantum well system. We measure the spectral diffusion of excitons within the inhomogeneously broadened line by time-resolved luminescence. We observe non-resonant flourescence line narrowing in these materials which leads to sharp lines sitting on top of the broad exciton luminescence. Using both lifetime and depashing measurements these lines are found to be predominantly luminescent in nature. The thermal broadening of the exciton due to longitudinal optical-(lO-) phonon scattering is measured up to room temperature and is found to be well-width dependent. The extent of the exciton localisation in this material can be deduced by a comparison of the depashing and spectral diffusion times with other systems.

Developments in the bulk growth of Cd 1−xZn xTe for substrates

Single crystal of CdTe or dilute alloys of Cd 1−yZn yTe (y < 0.04) and CdTe 1−zSe z (z < 0.04) with low defect density, high purity, and large single-crystal area (>30 cm 2) are required as substances for high-quality epitaxial Hg 1−xCd xTe thin films in the infrared (IR) detector industry. Bridgman or gradient freeze is the most common technique used for commercial production of these materials because of its success in producing large-area substrates of good quality and reproducibility. For epitaxial growth of Hg 1−xZn xTe, which has been of considerable interest in recent years as an IR detector material, the substrate of choice has been Cd 0.80Zn 0.20Te, for lattice matching with long-wavelength Hg 1−xZn xTe epitaxial layers ( x = 0.15). The primary focus of this paper is on CdZnTe, which is currently the preffered subtrate material and most widely used for both HgCdTe and HgZnTe epitaxy. This paper reviews the current status of bulk substrate technology for IR detector applications, highlighting critical issues and essential research areas for further improvement of these materials.

Growth of MgTe and Cd 1− xMg xTe thin films by molecular beam epitaxy

We report on the growth of the compound semiconductor MgTe as well as the ternary alloy Cd 1− x Mg x Te by molecular beam epitaxy. This is to our knowledge the first time that this material has been grown by any epitaxial technique. Bulk MgTe, which is hygroscopic, has a band gap of 3.0 eV and crystallizes usually in the wurtzite structure. Pseudomorphic films were grown on zincblende CdTe substrates for a MgTe thickness below a critical layer thickness of approximately 500 nm. In addition, Cd 1- x Mg x Te epilayers were grown with a Mg concentration between 0 and 68%, which corresponds to a band gap between 1.5 and 2.5 eV at room temperature. The crystalline quality of the layers is comparable to CdTe thin films as long as they are fully strained. The lattice constant of zincblende MgTe is slightly smaller than that of CdTe, and the lattice mismatch is as low as 0.7%. In addition highly n-type CdMgTe layers were fabricated by bromine doping. The tunability of the band gap as well as the rather good lattice match with CdTe makes the material interesting for optoelectronic device applications for the entire visible range.

NMR study of the diluted-magnetic-semiconductor alloys Cd1-xFexTe.

The diluted magnetic semiconductor alloys Cd 1-x Fe x Te, with x equal to 0.01, 0.02, 0.03, and 0.05, are studied by 113 Cd and 125 Te static and magic-angle-spinning (MAS) NMR spectroscopy at room temperature. The NMR spectra consist of frequency lines that are shifted by neighboring paramagnetic ions via the transfer hyperfine interaction. Assignments of all lines are suggested and their intensities are correlated to the probabilities of finding iron atoms in well-distinguishable conformational positions with respect to the observed nuclei. These assignments are consistent with a random distribution of magnetic ions in the zinc-blende crystal structure of Cd 1-x Fe x Te

Studies on infrared and photoluminescence properties of CdIn 2 O 4 films deposited by rf reactive sputtering

Transparent and conductive CdIn2O4 (CIO) thin films were prepared successfully by rf reactive sputtering from a Cd-In alloy target in an Ar+O2 atmosphere. The measurement of transmission and reflection spectra, at wavelengths between 0.2 and 6.0 μm, and photoluminescence spectrum of the films are reported. The optical properties of the films are analyzed and discussed in detail. Two reasonable methods for calculating the effective mass of the free carrier in the films are presented.

Observations of the effect of an applied stress on the morphology of discontinuous precipitation in a CuCd alloy

The influence of an applied tensile stress on the morphology and growth rate of the discontinuous precipitation product in a Cu−3.8 wt% Cd alloy was first reported by Sulonen. In this contribution, we investigate and further quantify a number of factors associated with the role of applied stress in this alloy, including absolute and relative growth rates of interfaces with normals parallel to and perpendicular to the tensile axis, and the morphological stability of discontinuous precipitation front as a function of the applied stress. Once morphological instability has occurred, the amplitude and wavelength of the protuberences formed depends on the value of the applied stress, and on the angle between the average interface normal and the tensile axis. It is suggested that the process is best viewed as one of transformation-assisted viscoelastic deformation.

Investigation of phase-transformation kinetics in electrodeposited Cu + Cd alloys using anodic linear sweep voltammetry

The anodic linear sweep voltammetry technique was used for a quantitative assessment of the phase composition of Cu + Cd alloys obtained by electrochemical deposition. Current peaks obtained in the voltammograms were attributed to the presence of particular intermetallic compounds known to exist in this system. It was found that alloys deposited by current densities exceeding the diffusion limiting current of Cu by several fold contain all the compounds recorded in the phase diagrams at an excess of pure Cd. The most dominant phase was found to be Cu 5Cd 8. It was observed that the voltammograms change with time, indicating that the freshly deposited alloys are unstable. Stabilization was found to take times in the range of 2 h. It is likely to occur in such a way that the excess Cd reacts with Cu-rich compounds to form CuCd 3. The method was found to be very sensitive to the presence of any particular phase. Thus CuCd 3, for example, could be detected at a level as low as 0.5%. The kinetics of the solid state reaction can be interpreted using the Johnson-Mehl equation. High values of the coefficient n indicate that nucleation of the new phase is a probable rate-determining step.

Dynamics of excitons in Cd xZn 1− xTe⧸ZnTe quantum wells

In this paper we detail the dynamics of intrinsic excitons in the alloy Cd x Zn 1− x Te⧸ZnTe quantum well system. Both single and multiple quantum well structures are studied. The strength of the thermal broadening of the exciton is measured up to room temperature and is found to be well-width and composition dependent. We also observe non-resonant fluoresence line narrowing in these materials which leads to sharp lines sitting on top of inhomogeneously broadened exciton luminescence at low temperature. Using both lifetime and dephasing measurements these lines are found to be predominantly luminescence in nature. We measure the spectral diffusion of excitons within the inhomogeneously broadened line by time-resolved luminescence. The extent of the exciton localization can be deduced by a comparison of the dephasing and spectral diffusion times with other systems.