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1.
Calorimetric and tunnel data for the icosahedral phases of the Al–Cu–Fe system have been jointly analyzed. It has been found that the field-dependent part of the tunnel conductance can be represented as the sum of elementary terms similar in nature to thermal Schottky anomalies. As a result, the features of the fine structure of tunnel spectra in the form of zero-bias anomalies, peaks, and humps can be due to the internal field emission and can indicate a wide distribution of two-level electron traps in the electronic structure of quasicrystals. It was previously assumed that these features constitute a direct image of the density of single-electron states of the conduction band. 相似文献
2.
M. V. Kuznetsov E. V. Shalaeva A. F. Prekul N. I. Shchegolikhina 《Bulletin of the Russian Academy of Sciences: Physics》2007,71(5):628-631
The electronic spectra of the valence band and core levels of the surface of polygrain alloys with the icosahedral structure and the β-(CsCl)-type solid solution of Al50Cu33Fe17 were investigated by X-ray photoelectron spectroscopy (XPS). The obtained XPS spectra of the Al62.5Cu25Fe12.5 alloy, in comparison with those of the crystalline Al50Cu33Fe17 alloy demonstrate narrowing and a decrease in asymmetry of the Fe2p core level and a decrease in the electron state density N(E F ) near the Fermi level, features expected for the poorly conducting icosahedral phase. The XPS data are compared with the estimates of N(E F ) based on the low-temperature specific heat measurements. 相似文献
3.
Experimental proofs are obtained for the fact that the intrinsic conductivity of quasicrystals at low temperatures satisfies
the T
3/2 law.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 4, 338–340 (25 February 1997) 相似文献
4.
A. F. Prekul V. A. Kazantsev N. I. Shchegolikhina R. I. Gulyaeva K. Edagawa 《Physics of the Solid State》2008,50(11):2013-2015
The mechanisms of energy absorption by metallic alloys with long-range aperiodic lattice order and electronic properties of marginal metals are studied. The heat capacity and linear expansion coefficient of the Al63Cu25Fe12 icosahedral phase in the temperature range 300–1000 K are measured for the first time. Disagreement between the measured heat capacity and predictions made from the Debye model is found and analyzed. It is shown that the excess heat capacity observed at the temperatures of the experiment is fitted by Einstein’s function in the approximation T ΘE.
相似文献
5.
A volume increase is observed at the ordering temperatures of icosahedral phases in samples of quenched alloys. The effect
is strongest in the systems that are closest to the boundary of the transition to the insulator phase.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 3, 190–195 (10 February 1998) 相似文献
6.
Conventional transmission and scanning electron microscopy were employed to investigate the structural state and phase transformations of the β(CsCl)-solid solution in rapidly quenched alloys of Al50Cu50? x Fe x with respect to the Cu/Fe ratio. We studied the alloys from the central (x?=?17 and 13) and border areas (x?=?6) of the β-solid solution homogeneity region. The structural state of the β-solid solution was characterized by premartensitic structural instability of the bcc lattice for x?=?17 and 13, and the presence of combined short-range order accompanied by the intense diffuse scattering for x?=?6. This short-range order can be described by the ordering of atoms and vacancies in the planes (111)β and ω-like atomic displacements (longitudinally polarized waves of displacement in the direction of the [111]β). The structural state of the β-solid solution with the combined short-range order was regarded as a pretransition state for the revealed transformation with homogeneous precipitation of the nanodispersed phase. The precipitation phase was attributed to an orthorhombic Al(Cu, Fe) η1-phase, belonging to the family of ordered β-based phases with orientation relationships of [100]η1 ||[110]β, [010]η1 ||[110]β, [001]η1 ||[001]β. We concluded that the atomic structure of the η1-phase is characterized by ordering, accompanied by ω-like atomic displacements of the adjacent layers in 3d metals (Cu, Fe) and aluminum. 相似文献
7.
E. V. Shalaeva A. F. Prekul S. Z. Nazarova V. V. Khiller 《Physics of the Solid State》2012,54(4):699-707
Electron microscopy has revealed that, upon the formation of a stable icosahedral (i) AlCuFe phase, there arise a large number of planar defects. The revealed defects are nanometer-sized coherent intergrowths
of the P1-pentagonal approximant. It has been found that the formation of these defects is the result of a nonequilibrium intermediate
transformation. The intergrowths are located in the planes with the fivefold symmetry axis and give rise to an elastic-strain
state of the i-phase. Analysis of the diffraction contrast has revealed the presence of phason and phonon atomic displacements due to the
mismatch between the quasiperiodic (i-phase) and periodic (P1-phase) lattices. The formed structure exhibits a higher electrical resistance as compared to the i-phase and has been considered as a model state of the imperfect icosahedral phase with preferred phonon displacements. 相似文献
8.
A.F. Prekul 《Physics letters. A》1978,64(5):473-474
Elementary dependences Tc(X) whose superposition describes a number of complex experimental situations are shown to exist. The concept of superconductivity-state diagrams is introduced, nine main types of such diagrams are being presented. 相似文献
9.
A. F. Prekul N. I. Shchegolikhina A. B. Gaiduchenko K. I. Grushevskii 《Physics of the Solid State》2011,53(10):1987-1990
The heat capacity of icosahedral quasicrystals Al63Cu25Fe12 and Al62Cu25.5Fe12.5 has been studied at high temperatures up to 1700 K, which is by almost 400 K higher than the melting point of the material.
It has been shown that the melt exhibits an excess heat capacity with respect to that determined by the Dulong-Petit law and
that is a direct extension of the excess heat capacity of the solid state. It has been concluded that the excess heat capacity
is related, as a whole, to the short-range order in the quasicrystal structure. This circumstance allows the identification
of the orbital hybridization as the most probable mechanism of formation of the pseudogap in the electronic structure of the
quasicrystals. 相似文献
10.
E. V. Shalaeva N. I. Medvedeva A. F. Prekul E. O. Smirnova S. V. Smirnov N. I. Shchegolikhina 《哲学杂志》2013,93(13):1024-1046
AbstractUsing transmission electron microscopy and X-ray diffraction, we established that the ordered η1-Al50Cu44Fe6 and φ-Al47.5Cu49.5Fe3 (Fmm2) alloys with nano-sized domain structure are formed by slowly cooling, whereas β-solid solutions with a short-range order were found in quenched states. The φ′-modification which exhibits the additional long-period superstructure was also observed in Al47.5Cu49.5Fe3. The studies of low temperature magnetic susceptibility and heat capacity did not reveal any another phase transitions in these alloys. The indentation test showed that hardness and Young’s modulus consistently grow as β-Al50Cu33Fe17 → η1-Al50Cu44Fe6 → (φ+φ′)-Al47.5Cu49.5Fe3 and approach to those in icosahedral phase. The same trend in the Young’s modulus was obtained for alloys containing β-solid solution with a short-range order. Ab initio calculations, however, predicted the opposite tendency in cubic β-Al50Cu50?xFex with a decrease in x, which was explained by the weakening of the covalent Fe 3d – Al sp bonding. This discrepancy between the results for β- and ordered phases, we related to a crucial effect of ordering which is accompanied by a progressive distortion of cubic local structure in the series β-Al50Cu33Fe17 → η1-Al50Cu44Fe6 → φ-Al47.5Cu49.5Fe3. As we demonstrated for η-Al(Cu, Fe), these distortions lead to the strengthening of the both covalent Fe–Al and Cu–Al bonds and the higher modules. 相似文献