Thermoelectric and electrical resistivity study of Hitperm alloys

Electron transport properties of amorphous alloys Fe_44.6Co_43.4X_7.3B_3.7Cu₁ (X = NbZr, Zr, HfZr, Hf) are studied by thermoelectric and electrical resistivity measurements. Thermoelectric power is dominated by the electron–magnon scattering whereas the magnetic component of electrical resistivity does not exceed 10%. The measured temperature dependencies of thermopower and resitivity are satisfactorily fitted to the Herzer and Richter models. For the Nb containing alloys the stronger electron localization and lower thermal stability are observed.     

Partial resistivity analysis of the NaK,NaRb and NaCs liquid alloys

The total resistivity for the NaK, NaRb and NaCs alkali alloys was divided into partial resistivities and calculated by means of Zimans’s formula within a simplified and semi-empirical approach. It is shown that the height of the parabolic resistivity behavior versus concentration is related to the scattering potential whereas the position of the maximum depends on the structure of liquid. Further it appears clearly that the leading contribution is due to the sodium as a result of its muffin tin zero enhancement with respect to its value in the pure liquid phase.     

Relationship between the short-range order and electrical resistivity in liquid indium-antimony

The composition dependencies of local structure and electronic structure, as well as the electric resistivity of liquid indium-antimony alloys have been investigated by the first-principles molecular dynamics simulations. It is shown that the variations of InIn, InSb and SbSb coordination tendency and the projected density of states of In and Sb in liquid In_xSb_1 ? x depend on the Sb concentration, and electric resistivity of liquid indium-antimony also reveals a regular change trends as a function of Sb concentration. Further analysis confirmed that there are explicit relationships between the short range structural parameters and electrical resistivities in liquid In_xSb_1 ? x.     

Effect of the magnetism of manganese on the resistivity of liquid manganese–zinc alloys

The electrical resistivity of liquid Mn_xZn_1−x alloys has been measured as a function of temperature between the liquidus and 850 °C for a manganese concentration x from 0 to 0.3. The electrical resistivity results has been interpreted within the extended Faber–Ziman formalism taking into account energy dependent phase shifts. Spin-dependent scattering of the conduction electrons has been considered and shows a better agreement with the experimental values than the classical spin-independent approach.     

Investigation of the microhardness and the electrical resistivity of undercooled Ni-10 at.% Si alloys

Ni-10 at.% Si alloys (Ni and Si of purity of 99.99%) were prepared by arc melting method under argon atmosphere in a water-cooled copper hearth with a non-consumable tungsten electrode and titanium getter. Spherical-shaped Ni-10 at.% Si alloy melts are undercooled in a containerless electromagnetic levitation apparatus. The effects of undercooling (ΔT) on the microstructure, electrical resistivity (ρ) and microhardness (HV) were investigated. The experimental results reveal that with the increase of the undercooling of the melts from 16 to 110 K, the microstructures undergo transition from coarse dendritic morphology to ultra fine dendritic morphology. The measurements of microhardness of the samples were performed by using a microhardness test device. The dependence of microhardness on undercooling was analyzed and it has been found that with increasing the undercooling the HV increases. Variations of electrical resistivity of the Ni-10 at.% Si alloy with the temperature in the range of 300-800 K were also determined by using a standard d.c. four-point probe technique. The resistivity of samples increases with increasing temperature and undercooling.     

Behavior of the resistivity of metal alloys during collective recrystallization

The kinetics of collective recrystallization in Sn-Pb, Sn-In, Sn-Zn, Pb-Sn, Pb-Bi, and Pb-In alloys have been studied using the conductivity method at T = 180°C.     

Structural properties of liquid Fe-Si alloys

The atomic structure of liquid Fe-Si alloys within the whole concentration range (including pure components) was investigated at the temperature of 1550 °C by means of X-ray diffraction. Analysis of the reported data on physical properties of Fe-Si melts has been carried out. Interrelation between liquid-state structure and solid-state properties was considered. Fe-Si alloys in the liquid state are shown to be micro-inhomogeneous and they contain atomic micro-formations (clusters) that differ by atomic composition and packing. There are five types of clusters: two of them consist of atoms of one kind (Fe or Al); the composition of the other clusters depends on the stoichiometry of solid Fe₃Si, FeSi and Fe₂Si₅ phases. The entire concentration range of the Fe-Si system consists of four concentration intervals. Within each interval melts are constituted of the clusters of two kinds. The variation of the component concentrations in Fe-Si alloys results in changing of volume fraction of each type clusters, whereas the atomic composition and arrangement inside the clusters remains constant.     

The structure of liquid Sb---Se alloys

The structure of liquid Sb_1-xSe_x alloys with x = 0.5, 0.6 and 0.7 was investigated in the temperature range of 600–800°C. The neutron diffraction measurements were carried out by using the high intensity total (HIT) scattering spectrometer of the booster synchrotron utilization facility (BSF) at the National Laboratory for High Energy Physics. A prepeak is observed in the structure factor for these three alloys. It suggests that the medium-range order stillo remains melting for liquid Sb_1-xSe_x alloys, with x = 0.5, 0.6 and 0.7. The structure factor liquid Sb₂Se₃ alloys shows no appreciable temperature variation. For liquid Sb_0.5Se_0.5 alloy, the intensity of the prepeak exhibits an apparent decrease in the temperature range in which the non-metal-metal transition occurs. The non-metal-metal transition in liquid Sb---Se alloys is due to the change in the medium range structure.     

Energetics of Cd-based binary liquid alloys

The thermodynamic properties such as, free energy of mixing (G_M), heat of mixing (H_M), entropy of mixing (S_M) and microscopic properties such as, concentration fluctuation in long wavelength limit (S_CC(0)), Warren–Cowely short range ordering parameter (α₁), ratio of mutual and intrinsic diffusion coefficients (D_M/D_id) of two Cd-based liquid alloys have been studied by using two different models. The properties of Cd–Hg liquid alloy at 600 K have been studied on the basis of regular solution model, and the properties of Cd–Na liquid alloy at 673 K have been studied on the basis of quasi-chemical expression for weakly interacting system.     

Principles of electrical behavior of amorphous semiconductor alloys

A new approach to understanding amorphous semiconductors is provided by a model whose novel concepts are necessary consequences of transport and recombination fundamentals. The amorphous semiconductors are examples of the ‘relaxation semiconductor’: When dielectric relaxation is slow compared with recombination, familiar transport behavior is drastically altered and the recombination characterized by cross sections for carrier capture which are extremely large. At thermal equilibrium, ‘equality recombination’ obtains, with which local space-charge neutrality is maintained through equal total capture rates of electrons and holes per unit volume. In the alloys, such recombination after single free paths gives equal electron and hole conductivities, and thus pins the Fermi level at the position of minimum conductivity for a given band gap. Both mean free paths are equal and of the order of the electron wavelength. They determine the concentrations of centers positively and negatively ionized, which are equal and large compared with mobile carrier concentrations. Nearly all the centers are neutral, are donors near the valence band and acceptors near the conduction band, and may be in fairly short band tails. The recombination is mainly at the deeper levels of the acceptor centers, which act also as shallow electron traps. On a simple and unified electronic basis, this model accounts in detail for the various aspects of observed behavior. The threshold switching is due to characteristics ‘recombinative injection’ of minority electrons. This produces a region of injected space charge in which the net recombination rate is zero, and puts at the anode an adjoining ‘recombination front’ of a type in which carriers are activated by field equal to the threshold field. Other aspects treated include, for example: the small negative Hall coefficient; the positive thermoelectric power; preswitching; delay time; integrated current or total charge during preswitching in its quantitative dependence on delay time; the ‘blocked ON state’; and the field effect, analysis of which gives the ionized concentration. The model has further implications for theory of the band structure.     

Structure of liquid Al-Cu-Co alloys near the quasicrystal-forming range

A local short-to-intermediate range order in liquid Al_63.9Cu_19.4Co_16.7, Al₇₁Cu₆Co₂₃, and Al_6oCu₂₉Co₁₁ alloys was investigated by X-ray diffraction technique and the reverse Monte Carlo modeling. A prepeak at Q ~ 17 nm^− 1originating from the unique bonding between the TM-TM pair (TM = Co, Cu) is observed in the structure factors of all investigated melts. The Voronoi-Delaunay analysis of RMC models indicates that a medium-range ordering of TM atoms in dense non-crystalline polytetrahedral clusters is associated with a chemical short-range order. The icosahedral short-range order is also closely related to the dense packing polytetrahedral clusters. A decrease of temperature leads to an enhancement of both chemical short-range order and icosahedral short-range order.     

Comparison of amorphous and liquid palladium-silicon alloys

The Pd_82,5Si_17,5 alloy has been investigated by X-ray diffraction in an amorphous state obtained by rapid quenching from the liquid state and also in the liquid state at a temperature just above T_f. The differences seen in the interference functions obtained relative to both states are not only due to a temperature effect. From the two atomic radial distribution functions it was possible to evaluate the Pd–Pd distances and the Pd–Si distances as well as the number of nearest neighbours. These distances have the same values, but the displacements of the atoms are more important in the liquid. The contribution of Pd–Pd bonds, for the metal-metal distances equal to 1.65 times the particle diameter, decreases in the liquid.     

The electrical and optical properties of amorphous germanium-gallium alloys

The paper extends an earlier study of the far infrared properties of a series of evaporated amorphous GeGa alloys. The results of temperature dependent dc resistivity and near infrared and visible optical experiments are presented. Since the properties of amorphous films are dependent on the preparation conditions, a technique has been developed in which four samples of varying composition are prepared in the same evaporation. The far infrared data indicate that a significant fraction of Ga atoms dissolve in a-Ge with four-fold coordination. However, there is also indirect evidence of mixed valence.     

Formation of atomic solution in liquid eutectic alloys

The influence of Pb, In, Bi and Ge on structure of tin within 0–12.5 at.% concentration range has been studied by means of X-ray diffraction method. Samples were prepared by melting in vacuum furnace filled with pure argon from ingots of Sn(99.999%), Pb(99.99), In(99.999), Bi(99.99), Ge(99.999) and checked by means of X-ray microanalysis The structure factors and pair correlation functions were analyzed. Concentration dependencies of structure parameters for liquid Sn-enriched melts in binaries with eutectic point are described. It is shown that atomic arrangement in tin-based molten alloy deviates from random atomic distribution within concentration range where these alloys can be considered as diluted solutions. Limited solubility in solid state in eutectic Sn-based systems is a precursor to deviation from random atomic distribution in liquid state.     

Threefold bonding of tellurium in liquid semiconductor alloys

Bond orbital considerations show that a third covalent band in tellurium is unstable unless the concentration of threefold bonded (3F) tellurium atoms is smaller than the concentration of dangling bonds. At low hole concentrations, the formation of 3F atoms is inhibited further because of non-linear screening of their positive charge, which results in a large electrostatic energy. Consequently 3F bonding becomes important only in liquids whose electrical conductivity is higher than an estimated value $\text{≈1500 Ω}{}^{\mathrm{?1}}\text{cm}{}^{\mathrm{?1}}$.     

X-ray diffraction measurements for liquid Ge–Si alloys using synchrotron radiation

Energy dispersive X-ray diffraction measurements have been carried out for liquid Ge_1−xSi_x alloys (x = 0.0, 0.3, 0.5, 1.0) using synchrotron radiation at SPring-8. We measured the X-ray diffraction spectra of liquid Ge and Si up to a high temperature range, (liquid Ge from 1270 to1870 K and liquid Si from 1680 to 2020 K), liquid Ge_0.7Si_0.3 at 1620 K, and liquid Ge_0.5Si_0.5 at 1540, 1590, 1670 and 1720 K. The total structure factors of the liquid Ge–Si alloys have a characteristic shoulder on the high-wave-vector side of the first peak. We deduced a pair distribution function from the Fourier transform of the observed structure factor, which was weakly dependent on the temperature. The nearest-neighbor coordination number of liquid Ge–Si alloys is close to that of pure liquid Ge and Si. The first peak of the pair distribution function moved to a shorter distance with increasing Si concentration. These results may indicate that the atomic radii of the Si and Ge atoms in the pure liquid are preserved in the liquid alloys.     

Electronic properties of vitreous and liquid AsSe alloys (II). Liquid alloys

Conductivity and thermopower data of liquid AsSe alloys with the same compositions as the vitreous alloys discussed in paper I (30–50% As) are presented and analysed assuming that the liquids can be regarded as ‘hot’ amorphous solids. The limitations of such an approach, as shown by the thermopower results, are discussed and improvements, based on structural and bonding arguments, suggested.