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1.
Measurements of the temperature- and magnetic field dependence of the electrical resistance of some metallic glasses are presented. The data obtained for Cu57Zr43, Cu40Zr60 and Pd30Zr70 demonstrate that deviations from the high temperature behaviour extrapolated to low temperatures are caused by superconducting effects. The paraconductivity which is strongly enhanced in amorphous alloys is shown to agree quite well with theoretical models. The normal state resistance does not saturate down to temperatures of about 2 K. It still exhibits a negative temperature coefficient of the resistivity.  相似文献   

2.
We measured the electrical resistivity (4–300 K), superconducting critical temperature and thermal conductivity (0.5–7 K) of the amorphous metals Zr70Cu30 and La70Cu30. Heat treatments below crystallization temperature induced changes in these properties. In particular, in the first stage of the annealing of Zr70Cu30 there are systematic changes in the thermal conductivity and the critical temperature, while the electrical resistivity remains constant. We show that there is no simple correlation between the thermal conductivity processes in the low temperature and plateau regions. We also show that the thermal conductivity of as quenched La70Cu30 is typical of amorphous metals, contrary to information previously reported.  相似文献   

3.
Summary A quadratic composition dependence of the electrical resistivity of amorphous transition metal alloys has been investigated at room temperature. A very good agreement between the theoretical and the observed values has been obtained in the case of NixZr1−x and CuxZr1−x for all compositions. The thermoelectric power was then correlated with the electrical resistivity satisfactorily for the CuxZr1−x and NixZr1−x To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.  相似文献   

4.
The low-temperature specific heat of freshly prepared and annealed amorphous alloys Zr70Be30, Zr67Cu33, and Zr75Rh25 has been investigated experimentally. The integral parameters of the electronic and phonon spectra have been determined: the Sommerfeld coefficients and the Debye temperatures. Data from calorimetric and neutron experiments were compared on the basis of the theory of lattices with off-diagonal disorder and localized modes. It is concluded that a local rearrangement of the structure occurs in freshly prepared samples as the temperature decreases. A model of a bistable impurity configuration is proposed to explain this restructuring. Fiz. Tverd. Tela (St. Petersburg) 39, 145–152 (January 1997)  相似文献   

5.
郭古青  杨亮  张国庆 《物理学报》2011,60(1):16103-016103
应用同步辐射X射线衍射(XRD)和广延X射线吸收精细结构边方法(EXAFS),结合反蒙特卡罗(RMC)拟合、Voronoi分形技术等对Zr50Cu50二元和Zr48Cu45Al7三元金属玻璃材料的微观结构进行了系统的研究.结果表明:ZrCuAl三元金属玻璃中Al原子与Zr原子、Cu原子之间存在强相互作用,表现为键长的明显缩短,导致其微观结构中的Voronoi团簇体积普遍小于Zr50关键词: 大块金属玻璃 原子结构 玻璃形成能力 同步辐射技术  相似文献   

6.
S R Jha  Y S Reddy  R G Sharma 《Pramana》1989,33(5):L615-L619
The thermoelectrical power (TEP) and the electrical resistivity behaviour of three 90 K superconductors viz, Y1Ba2Cu3O7−x , Sm1Ba2Cu3O7−x and Gd1Ba2Cu3O7−x , after the specimens were quenched from the sintering temperature (920°C) to 77 K, are reported. Interestingly the Y123 specimen, which has the presence of trace amount of the orthorhombic phase in an otherwise tetragonal phase and does not show a superconducting transition down to 77 K shows zero TEP around 82 K, theT c for the well oxygenated specimen. The Sm and Gd specimens on the other hand show completely tetragonal structure, semiconducting behaviour in resistivity and no zero TEP up to 77 K. It is argued that the critical concentration of the superconducting phase necessary to make the TEP zero is much smaller than that required for zero resistivity.  相似文献   

7.
曹忠胜  徐明  赵忠贤 《物理学报》1988,37(7):1167-1171
本文研究了金属玻璃(Cu1-xNix)33Zr67合金的低温电阻输运特性。在较宽的温区(2—273K)测试了电阻率,测量结果符合Mooij判据。样品电阻率随温度的变化行为与双能级隧道模型符合较好。 关键词:  相似文献   

8.
We report on the glass-forming ability and devitrification behavior of Zr60Cu30Al10, Zr60Cu25Al10Fe5 and Zr62.5Cu22.5Al10Fe5 bulk glass-forming alloys on heating. The effect of Fe addition on the structure of Zr–Al–Cu alloys is also discussed. Crystallization kinetics and structural changes in the glassy alloys were studied using X-ray diffraction, transmission electron microscopy, differential scanning and isothermal calorimetry methods. The results indicate that good glass-formers, such as Zr62.5Cu22.5Al10Fe5, are located somewhat beyond the equilibrium eutectic point. Possible phase separation in the supercooled liquid on heating and electron beam-induced in situ crystallization are observed and discussed.  相似文献   

9.
Measurements of the thermopower for amorphous alloys are reported in the temperature range 77K to 320K. The alloys examined are Cu50Ti50, Pd80Si20, Pd30Zr70 and Cu40Zr60. The data are compared with values of similar systems, as far as available. In addition we analyse the temperature coefficient of the thermopower, applying a model, based on the Ziman formulation of the transport properties.  相似文献   

10.
Cu-Zr-Ti系Cu基块体非晶合金的形成和成分优化   总被引:5,自引:0,他引:5       下载免费PDF全文
利用与团簇相关的变电子浓度判据研究了过渡金属Cu-Zr-Ti系中Cu基块体非晶合金的形成区域和成分特征.据此判据在Cu-Zr-Ti系相图中确定出三条特殊的成分线,(Cu9/13Zr4/13)100-xTix,(Cu0.618Zr0.382)100-xTix和(Cu0.56Zr0.44)关键词: 块体非晶合金 Cu-Zr-Ti合金 原子团簇 电子浓度  相似文献   

11.
Amorphous Zr50Al15−xNi10Cu25Yx alloy powders were fabricated by mechanical alloying at low vacuum with commercial pure element powders. The effects on glass forming ability of Al partial substituted by Y in Zr50Al15Ni10Cu25 and thermal stability of Si3N4 powders addition were investigated. The as-milled powders were characterized by X-ray diffraction, scanning electron microscopy and differential scanning calorimeter. The results show that partial substitution of Al can improve the glass forming ability of Zr50Al15Ni10Cu25 alloy. Minor Si3N4 additions raise the crystallization activation energy of the amorphous phase and thus improve its thermal stability.  相似文献   

12.
A variety of metallic glasses (CuxZr100?x with x = 30, 40 and 50, Ni24Zr76 and RE67 Co33, RE = Nd, Sm, Gd, Dy, Er) were studied using 2γ angular correlation techniques. Significant positron trapping is observed in all the glassy alloys investigated. The defect structure changes drastically during crystallization. For the RE-Co glasses the results suggest the existence of vacancy-like defects in the amorphous alloys.  相似文献   

13.
The orthorhombic Tb(Ni, Cu)2 and Gd(Ni, Cu)2 systems (CeCu2 structure) are closely similar according to electrical resistivity and magnetic results. The Tb(NixCu1?x)2 system presents a transition from antiferromagnetism (AF) for x ? 8% Ni to ferromagnetism (FM) for x > 8% Ni. The CeCu2 structure becomes unstable for x > 45% Ni. The AF samples show metamagnetism at 4.2 K with critical fields. Hysteresis, which occurs for all samples at 4.2 K, is attributed to intrinsic pinning due to large anisotropy where the mechanism for the AF range is analogous to intrinsic pinning of narrow domain walls in FM samples.Spin disorder resistivity measurements show a discontinuity at the AF-FM transition composition for both the Tb and Gd systems. This is due to a step up of the residual resistivity at 4.2 K as a result of AF ordering. This interpretation is confirmed by applying a magnetic field to destroy the AF ordering.  相似文献   

14.
The local magnetic, electronic, and structural properties of (RE)Ba2Cu3O7?δ supercondcutors (RE=Gd, Dy, and Eu) were studied by Mössbauer spectroscopy using the resonances of155Gd,161Dy,151Eu, and57Eu. In GdBa2Cu3O7?δ, different magnetic ordering behaviors of the Gd sublattice are found for the orthorhombic (superconducting) and tetragonal (non-superconducting) phases. In DyBa2Cu3O7?δ, the magnetic moments of the respective CEF ground states in the orthorhombic and tetragonal phases are derived from paramagnetic hyperfine splittings at 1.4 K. In both DyBa2Cu3O7?δ and EuBa2Cu3O7?δ, anomalies connected with the superconducting transitions in isomer shift, recoil-free fraction, and relaxation behavior were looked for, but not found. The electric-quadrupole splittings observed for both systems are discussed in connection with the lattice EFGs derived for the Gd system. In GdBa2 (Cu0.995Fe0.005)3O7?δ, the local properties of the various Fe sites are investigated over a wide temperature range in both the orthorhombic and tetragonal phase. The magnetic ordering of the Gd sublattice in the orthorhombic phase and of the Cu(2) sublattice in the tetragonal phase, respectively, is monitored via the magnetic splittings at the various Fe sites. Possible assignments of Cu(1) and Cu(2) sites as well as different oxygen configurations around the substituted Fe ions are discussed.  相似文献   

15.
In the present work, solid-state reactions in Sm2(Co, Fe, Cu, Zr)17-type alloys have been investigated by means of in situ electrical resistivity measurements. Changes in the electrical resistivity of a Sm(Co0.74Fe0.1Cu0.12Zr0.04)8.5 alloy after solid solution treatment at 1190 °C, quenching to room temperature, and during isothermal ageing at temperatures between 400 and 900 °C, have indicated microstructural/phase changes occurring at temperatures below those commonly used for the development of high coercivity in Sm(Co, Fe, Cu, Zr)z-type materials. Subsequent crystallographic and magnetic transition measurements have shown a high degree of correlation with respect to the changes observed in the electrical resistivity during isothermal ageing.  相似文献   

16.
In order to study the structural relaxation of the Zr60Al15Ni25 amorphous ribbon, the electrical resistivity was experimentally investigated. The changes in the resistivity before glass transition temperature were observed. Two temperature points (423?K and 573?K) were chosen for cyclic heating experiments. The results showed that both irreversibility and reversibility of structural changes existed in amorphous alloys, which were related to the selected temperature and cycle times. Based on the scattering mechanism of electron conduction in metal, the structural defects model was used to explain the changes of electrical resistivity. The sample was in a highly disorder state after experienced thermal cycling of high temperature (573?K). The number and kind of atoms may be changed to increase the crystallisation range.  相似文献   

17.
Binary icosahedral and crystalline phases of the Zr70Pd30 alloy were obtained in crystallization from the amorphous state during heat treatment. The specific heat and electrical resistivity of the icosahedral, amorphous, and crystalline phases were measured and compared. An increase in the electronic density of states on the Fermi surface, lattice softening, and an increase in the electron-phonon coupling constant were observed to occur with decreasing structural order. Despite the high valence electron density in the icosahedral phase, where the electronic densities of states are twice those in the crystal, the electrical resistivity of the icosahedral phase is ~50 times as high. Superconductivity was observed for the first time in the icosahedral phase of a binary system of transition metal atoms, Zr70Pd30.  相似文献   

18.
Electrical resistivity, ?, has been measured as a function of temperature, T, of Cr alloys containing 0.47, 0.93, and 1.63 at.% Pt. The onset of antiferromagnetism causes anomalies in the ? vs T curves which increase with increasing Pt concentrations. Using the criterion that at the Néel temperature, TN, d?/dT is minimum, it has been determined that the values of TN are (430 ± 10)K, (490 ± 5)K, and (535 ± 5)K for the above-mentioned alloys. The nature of the antiferromagnetic state and the corresponding anomalies in the electrical resistivity in the Cr-Pt system are very similar to those found in Cr-Ir solid solutions.  相似文献   

19.
测量了块体金属玻璃Zr46.75Ti8.25Cu7.5Ni10Be27.5在退火前后其电阻值随温度的变化,测量的温度范围为1.5—300K.样品在退火前后都发现有超导现象.零磁场下其超导转变温度Tc分别为1.84和3.76K.在5—300K温度范围内,原始样品具有负的电阻温度系数.如果取Zr, Ti, Cu, Ni及Be分别贡献出1.5, 1.5, 0.5, 0.5及两个传导 关键词: 块体金属玻璃 超导 电阻温度系数  相似文献   

20.
Measurements of the current-voltage characteristics on point-contacts, of the thermopower and the thermal conductivity between 1.3 and 300 K and of the electrical resistivity between 4.2 and 900 K of polycrystalline samples of ReCu6 (RE=La, Ce, Pr, Gd) are presented. The anomalies of the heavy fermion system CeCu6 are strong compared to the other systems, but the properties of LaCu6 and PrCu6 are also unusual, possibly caused by the complicated crystal structure and, for PrCu6, by crystal field effects.  相似文献   

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