Fig 6 - uploaded by Jean-Georges Gasser
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Electronic density of states (DOS) versus electron energy in five different Al 1Àx Mn x alloys corresponding to spin-up contributions (long dashed line), spin-down contribution (short dashed line) and total DOS (solid line). The vertical line indicates the locations of Fermi energy, E F .
Source publication
We present experimental measurements of resistivity and thermoelectric power of liquid alloys, Al1-x-Mnx, (x = 0.12, 0.14, 0.16, 0.18, 0.20). The resistivity increases from 28.88 μΩ cm for pure aluminum to 123.3 μΩ cm for the alloy. No resistivity extremum is observed near the Mn concentration x = 0.14, in contrast to that observed in the quasi-cry...
Contexts in source publication
Context 1
... DOS profiles are calculated by the differentiation of Eq. (6) with respect to energy and are plotted in Fig. 6. The Fermi energy, E F , can be obtained via Eqs. (7) and (8), for Z all ¼ N(E F ), where N(E) represents the integrated DOS. It is important to mention that the calculations of electronic and thermoelectric properties of the alloy must be carried out at the Fermi level, E ¼ E F ...
Context 2
... Fig. 6, we observe a shift of about 0.1 Ryd between the two peaks of DOS attributed to the states of spin-up and spin-down of Manganese. The two main peaks of DOS corresponding to up and down spins are relatively wide because of the overlapping resonances peaks of the two configurations of Manganese. The low energy region of DOS is comparable ...
Context 3
... to those reported by other authors [21,22] who found energy gaps around 0.19 Ryd between the DOS peaks attributed to spin up and spin down states. In the frame of our model, the existence of energy gap of 0.19 Ryd might be justifiable as it can be attributed to the Mn3 configuration but it is hidden in the wide peak of the total DOS. Moreover, Fig. 6 shows a wide main peak of the total DOS profile for all Al 1Àx Mn x alloys. For each alloy composition, we have located the Fermi level at E F ¼ 0.61 Ryd. This value remains unchanging for all alloy compositions which can be attributed to the compensation effect between the increasing of the Manganese peaks and the decreasing of ...
Context 4
... Fig. 7 we present the resistivity r(E) as a function of energy. As outlined in our theoretical model, the shape of the resistivity curve is homothetic to the total DOS shown in Fig. 6. To asses the accuracy of r(E) versus E graphs, we plotted the experimental resistivity as horizontal line as it has no energy dependence. Also theoretical values of resistivity, calculated at the Fermi energy, are marked by open circles. We also write the measured and calculated values of TEP. Both values has negative sign which ...
Citations
... These results are compatible with the basic Al-Si-Mg eutectic alloy results in our study. In a similar study, Ben Abdellah et al. 63 investigated the change in electrical resistivity with the change of Mn amount in Al-Mn alloy, and in this study, they observed that the electrical resistivity increased strongly with the increase in Mn amount. In our study, the increase in electrical resistivity with the increase in Mn addition from 0.5 to 1.5% can be explained by the increase in the amount of Mn in the solid solution and the accumulation of Mn and impurity atoms in the increased grains with the grain reduction effect of Mn. ...
The study added Mn at different rates to the Al–Si–Mg eutectic alloy and heat-treated the quaternary alloy. Therefore, the microstructure morphology of the Al–Si–Mg eutectic alloy was examined after Mn addition and heat treatment. Also determined were the hardness, tensile strength, fracture surface analysis, and thermoelectric characteristics of the newly produced Al–12.95%Si–4.96%Mg–X%Mn [X=0.5, 1.0, and 1.5 (wt.)] alloys. Along with the predicted Si and Mg2Si phases in the Al matrix phase, this investigation found a randomly distributed Mn-rich Al15Mn3Si2 intermetallic phase and a Mg-rich Al5Si3Mg2 phase. Mn-doped samples without heat treatment were somewhat softer than the parent alloy. After heat treatment, the hardness more than doubled for the Al–Si–Mg eutectic system and Mn-doped samples. After heat treatment, the alloy with 1.5% Mn added had the maximum hardness value of 94.3±5.0 HV. Heat treatment improved tensile strength by up to 80%, and the alloy with 0.5% Mn had 144.7 MPa. Melting temperatures (Tm) (K), fusion enthalpy (ΔH) (J/g), and specific heat Cpl (J/gK) were determined for non-heat-treated materials. The 0.5, 1.0, and 1.5 Mn-added samples had Tm of 566.30, 568.96, and 566.40 °C, respectively. The ΔH value of samples with 0.5%, 1.0% and 1.5% Mn addition is 662.29, 657.93 and 639.11, respectively. Cpl was 0.788, 0.781, and 0.761 J/g.K. for 0.5%, 1.0%, and 1.5% Mn-added samples. In both heat-treated and non-heat-treated samples, Mn enhanced electrical resistance.
... In the t-matrix formulation, electrical resistivity of liquid binary alloys is calculated using following equation [30][31][32]. ...
... In another approach of Esposito et al [36], the authors have determined Fermi energy by neglecting E b term. The authors in [32] have determined Fermi energy by introducing effective valence as a parameter. In the present work, we propose a slight alternative approach. ...
... It is observed that zeroth order phase shift (s-phase shift) contribute maximum at lower energy and at higher energy values, contribution is more from first and second order phase shifts. Presently calculated energy dependent electrical resistivity of pure Pb and Li are shown in figure 3 along with the results of Abdellah [32]. In their approach, Abdellah et al have determined Fermi energy with respect to MT zero potential and have taken E B ≠ 0. Further, they have used effective valence as a parameter in their calculation. ...
It is generally observed that electrical transport properties of simple liquid metal based alloys can be explained well in terms of Faber-Ziman theory, 2kF scattering model and finite mean free path approach. However, these approaches give poor description for materials, which show departure from nearly free electron (NFE) model. Taking Pb-Li as a test case of a system showing departure from NFE (which also exhibit compound formation tendency and disparate mass system), a new technique is proposed to compute electrical transport properties using model potential formalism coupled with t-matrix formulation. We have treated valence number of Pb & Li as a parameter in determining phase shifts. Further, rather than calculating phase shift in terms of Muffin-Tin potential, we have used model potential formalism. Present results suggest that compared to other three theoretical approaches mentioned above, present coupling scheme reproduce qualitative features of electrical transport properties of liquid Pb-Li alloys, which can be used further to study electrical transport properties of similar systems.
... In this work, online thermopower measurement provides the real-time and continuous check for the melt, as well as a new insight into the phase evolution treated by magnetic field. Electrical parameters depended on temperature have been theoretically and experimentally investigated by many researchers [23,24]. Meanwhile, the electrical parameters of liquid metal have gradually drawn much attention to reveal the melt structure variation, even in the external fields [25][26][27][28]. ...
Magnetic field is an effective strategy to refine microstructures, however, few researches focus on refinement efficiency over the different temperature ranges. In this paper, we develop the online thermopower measurement to provide the real-time and continuous check for the melt treated by alternating magnetic field over the selected temperature ranges. The effects of alternating magnetic field on eutectic and primary phases of Al-Fe binary alloy are discussed by both the thermopower and the solidification microstructures. Thermopower-temperature coefficient α =dS/dT turns from 0.1565 μV·K⁻² to 0.0259 μV·K⁻² at liquidus due to the solid particles precipitation during the direct cooling process without treatment. Relationships of thermopower and temperature are given to display the kinetics process. Thermopower increases with violent oscillation during the magnetic field. From the results of microstructures, magnetic field induces the promoted nucleation and decreased spacing of needle eutectic phases, as well as the refinement of bars and blocks primary phases, which strongly depends on the temperature ranges. Thermopower responds to nucleation and growth of eutectic and primary phases. This should be mainly attributed to the solid particles precipitation and the thermoelectric magnetic effects, respectively. Meanwhile, thermopower can be used to respond the microstructure evolution.
... A variation in the slope is also an indicator of a phase change of matter. Some experimental results obtained via these characterization methods (resistivity and ATP) can be compared to those calculated by various theoretical elaborated models [11,12]. ...
Electron transport properties and thermal stability of Ni33.3Zr66.7 metallic glass (MG) have been studied using an original device for simultaneous measurements of electrical resistivity and absolute thermoelectric power (ATP) controlled by a LabView software written by one of us. The electrical resistivity and absolute thermoelectric power were measured simultaneously and very accurately over a temperature range from 25 to 400°C with a nominal heating rate of 0.5K min⁻¹. The electronic thermal conductivity was also determined using the Wiedemann-Franz law in the same temperature range. Due to its high efficiency, this technique is more and more used because it is characterized by a high sensitivity to detection of the phase transitions related to electronic transport, which is the aim of this study. Analysis of the temperature dependence of the resistivity and ATP of the Ni33.3Zr66.7 glassy ribbons proves the potential of this characterization method to study the thermal behavior of metallic glasses. The crystal structure and the morphology of Ni33.3Zr66.7 metallic glass in the as-quenched state and after heat treatments were studied using X-ray diffraction (XRD), and scanning electron microscope (SEM).
... So S increases in the AC MF, and then shows the recovery process and differences from initial values. The distribution function r k f , ( ) in the electromagnetic and temperature field shows that the determination of S (is also the Fermi energy, deleted) attributes to the density of states in the alloys [35]. From microscopic points, changes of clusters affect the density of states, which is reflected by the scattering variation in the electron transport. ...
The melt structure of Al-0.99 wt.% Fe alloys in the AC magnetic field have been studied with thermoelectric power by the four-point probe technique and microstructure with the liquid quenching method. The melt temperature is in the range of 913 K-1013 K. The thermoelectric power increases due to the AC magnetic field and decreases after the AC magnetic field stops, then keeps stable. Some characteristic parameters of thermoelectric power in the recovery process are used to represent the variation of melt structure. The α-Al phase refinement in the AC magnetic field is attributed to the persistent variation of melt structure. The persistent variation of thermoelectric power can be used to characterize the variation of the α-Al phase size. The hardness increases and the diffraction peaks of some planes reduce, which can reflect the uniform and disorder melt structure in the AC magnetic field.
The electrical resistivity and the thermoelectric power of liquid metal Cs have been theoretically investigated using the muffin-tin potential approach with the help of an accurate experimentally measured structure factor, S(q), and radial distribution function, g(r) measured along the liquid–vapour coexistence curve. Our procedure provides a clear evidence of the existence of metal–non-metal transition in the temperature region 1500–1800 K. Furthermore, this transition was apprehended by monitoring the shift of the position of the Fermi energy relative to the muffin-tin-zero potential, as well as the effective number of conduction electrons, N c, in the conduction band.
Some of mechanical, electrical, and thermal properties of the Al–(Nb, Mo, Ta, W) binary thin films which are important for the stability and usability of the amorphous alloys were examined. Samples were prepared by magnetron deposition technique in wide range of composition onto various substrates held at room temperature. Different experimental techniques were used for the characterization of samples. The results of structural relaxation and crystallization measurements under isochronal conditions are compared with the results of measurements of micro/nano hardness and strain in the films. From the micro/nano hardness measurement, the elastic deformation energy fraction is calculated. The elastic deformation energy fraction is correlated with the various results obtained from electrical resistivity measurements under isochronal conditions. Particular emphasis was placed on the Al–Mo amorphous alloys. It turns out that elastic deformation energy fraction becomes important indicator and phenomenological correlation parameter between various physical properties of examined films.
