Methods for determination of effective diffusion coefficients in ternary alloys (II). Indirect methods of calculating ternary diffusion matrix

We summarised, in part one of this paper, procedures of measuring diffusion matrix in three-component single phase alloys direct from the concentration-distribution profiles in infinite diffusion couples. In this paper (Part II) some procedures have been outlined which enable calculate ternary diffusion matrix from easily measurable tracer coefficients in ideal and non-ideal single phase solid solutions. These procedures have been illustrated with examples, so that it becomes apparant that in many cases the experimental difficulties faced by the experimentalists in direct measurement of ternary diffusion coefficients can be reduced to a large extent.     

Configuration entropy of ternary alloy superlattice

Difference in mixture-related entropy between superlattice and the corresponding homogeneous crystal in which all composition gradients have been annihilated by equilibrating processes (the configuration entropy of superlattice, ΔS_conf) is analytically formulated as a function of composition variables and geometry parameters. Numerical evaluations are performed for the important case of Al_xGa_1−xAs-based superlattice. Qualitative trends confirm in general the intuitive expectations (− ΔS_conf grows with increasing composition difference between the layers); the dependencies on geometry parameters exhibit a peculiar behaviour. The results are applicable to superlattices with periode lengths sufficiently in excess of the monoatomic layer thickness.     

Determination of thermal diffusion coefficient and diffusion coefficient

A new technique is described to determine the thermal diffusion coefficient, D', and the difusion, D, of Fe, Si and Al in liquid Mg. This technique is based on a boundary condition, formulated by including contributions of temperature and cocentration gradients in the liquid to the advancing solid-liquid interface during unidirectional solidification of a binary alloy. The determined values of D'_Fe, D'_Si and D'_Al are 5.57 × 10^-6, 7.35 × 10^-6 and 3.64 × 10^-6 cm/sec °C and D_Fe and D_Si are 1.9 × 10^-5 and 1.5 × 10^-5 cm²/sec, respectively.     

Dielectric properties of ternary melt processed blends

Thermal, morphological and dielectric properties of conductive thermoplastic blends based on polystyrene, styrene–butadiene–styrene block copolymer and doped polyaniline have been investigated with special emphasis on the effect of doped polyaniline concentration. Blends were prepared by melt blending using an internal mixer. Morphological studies by scanning electron microscopy of cryofractured surfaces indicated that thermoplastic matrix had a better miscibility with the presence of copolymer as compatibilizer and also good dispersability and structuring of doped polyaniline particles within polystyrene. A reduction in impedance from 26 to 2 MΩ at 10 Hz, with the increasing polyaniline content is also observed. The blends can be used for antistatic applications. From the fit to the impedance spectroscopy data we obtained the relaxation strength, the depression angle and the relaxation.     

Superconducting state parameters of ternary amorphous superconductors

The theoretical investigations of the superconducting state parameters (SSP) viz. electron-phonon coupling strength λ, Coulomb pseudopotential μ^?, transition temperature T_C, isotope effect exponent α and effective interaction strength N_OV of (Ni₃₃Zr₆₇)_1 − xM_x (x = 0, 0.05, 0.1, and 0.15, M = Cu) ternary amorphous superconductors have been reported using Ashcroft's empty core (EMC) model potential. Five local field correction functions proposed by Hartree (H), Taylor (T), Ichimaru-Utsumi (IU), Farid et al. (F) and Sarkar et al. (S) are used in the present investigation to study the screening influence on the aforesaid properties. The T_C obtained from Sarkar et al. (S) local field correction function is found in excellent agreement with available theoretical data. Quadratic T_C equation has been proposed, which provides successfully the T_C values of ternary amorphous alloys under consideration. Also, the present results are found in qualitative agreement with other such earlier reported data, which confirm the superconducting phase in the superconductors.     

The coherent phase diagram of AIIIBv ternary system

The equations of the coherent phase diagram for A^IIIB^V ternary system are derived in suggestion of simple solution model. The system Ga-As-P is analyzed in details. The solubility of GaP and GaAs in liquid phase Ga-P-As of different composition has been investigated. The stabilisation effect of solid solution composition has been quantitatively described using the system Ga-In-P.     

Melting temperature and debye temperature of ternary chalcopyrite semiconductors

Band state concept has been used for the first time to explain the Melting temperature and Debye temperature of ternary chalcopyrite semiconductors. The experimental results agree quite well with those evaluated from this model. Finally we derive a correlation between the two termperatures.     

Magnetic and electric properties of the ternary alloys AB

The results of experimental studies of the electrophysical and magnetic properties of solid solutions based on the AB compounds with anion (Zn₃(P_xAs_1−x)₂ and cation (Zn_xCd_1−x)₃ P₂ substitution are reported. The Zn₃(As_xP_1−x)₂ solid solutions are characterized by p-type conductivity (∼ 10¹⁵  10¹⁷ cm⁻³), low Hall mobility and conductivity of ∼ 10⁻² — 10⁻³ ohm⁻¹ cm⁻¹. In the (Zn_xCd_1−x)₃P₂ solid solutions the samples rich in zinc are p-type, those rich in cadmium — n-type, the carrier concentration is ∼ 10¹⁶ — 10¹⁸ cm⁻³. From the measurements of the magnetic properties of the above mentioned alloys it is shown that in the investigated solid solutions a transition from the structure with direct optical transition to those with indirect optical transition occurs.     

Calculation of composition variation of In1−vGavAs ternary crystals for diffusion and electromigration limited growth from a temperature graded solution with source material

A theoretical model was proposed to calculate composition variation of III-V ternary crystals during growth. In this model, for the first time, phase equilibrium between crystal and growth solution is maintained together with constancy between the transported and incorporated mass or solute atoms at the crystal/solution interface at the same time. This model can be applied to the calculation of the diffusion and electromigration limited growth in a temperature-graded solution with source material such as the source-current-controlled (SCC) growth method. The composition variation of In_1−vGa_vAs crystals grown by diffusion and electromigration was calculated by this model. Incorporation of two kinds of solute elements, Ga and As, into crystals through the crystal/solution interface was considered on the basis of the laws of the phase equilibrium and the constancy of mass. In comparison of the experimental results with the calculated ones, it is found that in the In-Ga-As solution the diffusion coefficient of Ga, D_Ga, is about two times as large as that of As, D_As, and μ_Ga is larger than μ_As. The calculated results of the composition variation show that the composition uniformity in In_1−vGa_vAs crystals can be largely improved by controlling the growth parameters such as temperature gradient in the solution, solution length, existence of source material, and electric field.     

Reentrant lyotropic nematic phase in a ternary mixture

We report the results of our studies on optical and thermal properties of ternary mixture of three compounds viz., 4′-n-octyl-4-cyanobiphenyl (8CB), didodecyl dimethyl ammonium bromide, and glacial acetic acid. Higher concentrations of the given mixture show a very interesting reentrant nematic phase, sequentially when the specimen is cooled from its isotropic melt at different temperatures. The temperature variations of optical anisotropy, optical textures, and electrical conductivity have also been discussed. Nanoaggregated size of the molecules has been confirmed by X-ray studies.     

Strength and fatigue of some binary and ternary silicate glasses

A survey represented mainly by means of glasses of the borosilicate system shows the generally valid limits of the applicability of the crack growth model and the essential influence of the corrosion of glasses on fatigue. A close correlation between macroscopic crack growth and fatigue was affirmed for samples with fresh, slightly corroded cracks. If the state of corrosion of the samples is advanced, the influence of region 2 is reduced and the fatigue limit is increased. Processes of corrosion during the measurement influence the fatigue curve prevailingly in the range of great time-to-failure, in particular the slope in region 1. The results indicate the high complexity of the effective chemomechanical processes during the fatigue measurements.     

Glass formation of ternary CaCuMg alloys

Ternary CaCuMg alloys have been investigated with respect to their glass forming ability. Intermetallic glasses can be obtained for all constituting binary systems. The ternary system exhibits one extensive range of glass formation, interconnecting the binary ones. Differential scanning calorimetry has been applied to study thermal decomposition of the glasses obtained. Conditions of formation are discussed in the light of thermodynamic and kinetic criteria.     

Bandgap characters in GaAs‐based ternary alloys

The existence and origins of the bowing character in the bandgap variation of GaAs‐based ternary alloys are theoretically investigated based on two different computational methods. Within the framework of the virtual crystal approximation (VCA), both the empirical sp³s * tight‐binding (TB) method with, and without, the inclusion of the spin‐orbit coupling effects, and the first‐principle full‐potential linear augmented plane wave (FP‐LAPW) technique are applied on both the common‐cation GaSb_xAs_1‐x and the common‐anion Ga_1‐xIn_xAs alloys. These methods are used to calculate the bandgap energy, the partial and total densities of states and the constituent charge ionicity versus the composition x. The results show that the bowing behavior exists in the case of common‐cation alloys (GaSb_xAs_1‐x) as a manifestation of a competition between the anion atoms (As and Sb) in trapping the made‐available‐cationic charges. The bowing parameter is found to be proportional to the electronegativity characters of the competing anions (χanion). Consistent with this in the case of common‐anion alloys (Ga_1‐xIn_xAs), as due to the lack of anion competition, the bowing is just absent and the variation of bandgap energy is found to be rather linear. The excellent agreement between our theoretical results and recent photoluminescence data has corroborated our claim. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Kinetics of crystallization of titanium based binary and ternary amorphous alloys

Metallic glasses are kinetically metastable materials. These amorphous materials can be transformed into a crystalline state by both isothermal and isochronal methods. The study of this transformation, and hence the thermal stability of metallic glasses, are important from an application view-point. In the present work, the non-isothermal crystallization kinetics of two titanium-based amorphous alloys namely, Cu₅₀Ti₅₀ and Ti₅₀Ni₃₀Cu₂₀, are reported. The activation energies for crystallization, E_c for both the systems have been evaluated using different non-isothermal methods viz. derived through Kissinger, Augis and Bennet and Ozawa. The values of E_c obtained using these methods are consistent for both the metallic glasses and it is found that E_c for the ternary metallic glass is considerably higher than the binary metallic glass. The increase in the activation energy on the substitution of Ni in the Cu–Ti metallic glass suggests the increase in the thermal stability.     

Adiabatic bond charge model for lattice dynamics of ternary chalcopyrite semiconductors

The adiabatic bond charge model of Rustagi and Weber is extended to study lattice dynamical properties of ternary chalcopyrite semiconductors AgGaS₂, AgGaSe₂, CuInS₂, CuInSe₂, CuGaS₂, CuGaSe₂, CuAlS₂ and CuAlSe₂. The new model calculations agree well with the results of Raman/IR and neutron measurements of Brillouin zone center phonon frequencies for both low and high frequency modes which was difficult for other phenomenological lattice dynamical models. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Experimental studies of phase equilibria in high-temperature ternary immiscible metallic melts

Shear viscosity measurements were carried out for a liquid immiscible ternary system In–Se–Te in a temperature range from the monotectic to about 1200 K using an oscillating-cup viscometer. It was revealed that the ternary In₈₀Se_xTe_20−x (0 ⩽ x ⩽ 20 at.%) system may be considered as a set of quasibinary In–(Se/Te) alloys of almost critical concentrations. A variation of the Se to Te ratio at constant content of In changes the properties of coexisting liquids and affects the binodal temperature. The critical parameters describing the peculiarities of viscosity behavior in the vicinity of the critical point are evaluated. The analysis based on the dynamic theory of phase transitions for viscosity in the phase separation region is proposed. The results are compared with available data for immiscible dielectric solutions and metallic melts.     

Fracture toughness-composition relationship in some binary and ternary glass systems

Measurements of the critical stress intensity factor K_Ic are reported for glasses in the Na₂OSiO₂, PbOSiO₂, ZnOB₂O₃, PbOB₂O₃, Na₂OGeO₂ and 20Na₂O?(80 ? x) B₂O₃ ? xSiO₂ systems. The variations of K_Ic with composition are not directly related to the simultaneous variations of Young's modulus. A tentative interpretation is given.