Electrical properties of exchange-enhanced systems: Co in (Pd95Rh5)

The electrical resistivity of several (Pd₉₅Rh₅)-based alloys containing between 1.1 and 2.6 at % Co has been measured up to 300K. In alloys containing between 1.4 and 2.6 at % Co the incremental resistivity δ?(T) is found to contain a Tsu2 term at low temperatures, as previously found for comparable amounts of Fe in the same host, and from which it is inferred that the restoration or removal of wave vector conservation for electron-magnon scattering in this type of system is not a mean-free-path effect. Estimates of the acoustic spin-wave stiffness are derived from the measured Tsu2 terms. These resistivity data also enable the magnetic ordering temperatures T _c and the s-electron- and d-electron-local moment exchange couplings J _s-local and J _d-local to be estimated. Differences in the behavior of the incremental resistivity δ?(T) in the paramagnetic regime of (Pd₉₅Rh₅)Fe and (Pd₉₅Rh₅)Co systems are tentatively discussed in terms of the possibility of localized spin fluctuations at the Co sites.     

Electrical properties of non-stoichiometric PZT 95/5 ferroelectric ceramics

Pb_0.99(Zr_0.95Ti_0.05)_0.98Nb_0.02O₃ (denoted as PZT 95/5) ceramics were prepared according to the nominal composition of Pb_0.99+x (Zr_0.95Ti_0.05)_0.98Nb_0.02O_3+x (?0.01 ≤ x ≤ 0.04). The electrical properties as a function of lead oxide (Pb) stoichiometry were evaluated. X-ray diffraction analysis shows that all the as-synthesized PZT 95/5 powders are pure perovskite phase and the unit cell volume increases with the addition of Pb. SEM micrographs indicate the fracture mode tends to be predominately intergranular and grain size gets bigger with the increase of Pb content. The coercive field decreases with the increase of Pb till x = 0.02 and then increases when the excess Pb is over x = 0.02. The remnant polarization first increases and then decreases with the increasing amount of excess Pb. Sample with excess Pb x = 0.03 has the biggest value of remnant polarization.     

Electrical properties of LaBi8Fe5Ti3O27

LaBi₈Fe₅Ti₃O₂₇, an important member of the family of bismuth layered structure ferroelectromagnetics, was prepared by a standard high-temperature solid-state reaction technique. Preliminary X-ray structural analysis exhibited the formation of single-phase compound with an orthorhombic structure. Scanning electron micrograph of the material exhibits the uniform grain distribution throughout the sample. Dielectric measurements were also performed on these samples. Combined impedance and modulus plots were used as tools to analyze the sample behavior as a function of frequency. The dc and ac conductivity measurements were performed on the samples.     

Electrical properties of LiNi3/5Fe1/5Cu1/5VO4 ceramics

In this work, LiNi_3/5Fe_1/5Cu_1/5VO₄ ceramic was prepared by solution-based chemical route whose X-ray diffraction results reveal an orthorhombic unit cell structure with lattice parameters of a = 9.6329 (23) Å, b = 6.8527 (23) Å, c = 5.4667 (23) Å. Complex electrical impedance and electrical conductivity were studied using complex impedance spectroscopy technique. The analysis of complex electrical impedance shows: (i) grain interior, grain boundary and electrode-material interface contributions to electrical response and (ii) the presence of temperature dependent electrical relaxation phenomena in the material. A detailed study of electrical conductivity indicates that electrical conduction in the material is a thermally activated process.     

Microstructure and mechanical behaviour of (Fe88Si12)95Al5 alloy prepared by aluminothermics

Abstract

The (Fe₈₈Si₁₂)₉₅Al₅ alloy was prepared by an aluminothermics. The (Fe₈₈Si₁₂)₉₅Al₅ alloy is composed of spheroidic α-Fe(Si,Al) precipitate with size of 20–50 nm and γ-Fe(Si,Al) matrix. The yield strength and fracture strain in compression of the (Fe₈₈Si₁₂)₉₅Al₅ alloy are 1500 MPa and 23% respectively. The shear bands propagating in the compressive deformation are arrested by the precipitation particles that resulted in large ductility and high strength simultaneously.     

Pd/GaN(0001) interface properties

This report concerns the properties of an interface formed between Pd films deposited onto the surface of (0001)-oriented n-type GaN at room temperature (RT) under ultrahigh vacuum. The surface of clean substrate and the stages of Pd-film growth were characterized in situ by X-ray photoelectron spectroscopy (XPS), scanning tunneling microscopy (STM), ultraviolet photoelectron spectroscopy (UPS), and low energy electron diffraction (LEED). As-deposited Pd films are grainy, cover the substrate surface uniformly and reproduce its topography. Electron affinity of the clean n-GaN surface amounts to 3.1 eV. The work function of the Pd-film is equal to 5.3 eV. No chemical interaction has been found at the Pd/GaN interface formed at RT. The Schottky barrier height of the Pd/GaN contact is equal to 1.60 eV.     

Superconducting and magnetic properties of ternary silicides in some rare earth-noble metal (Rh or Ir)-silicon systems

New families of ternary silicides have been prepared in the RE - Rh or Ir -Si systems and the crystal structures have been determined: RERh₃Si₂, RE₂Rh₃Si₅, RE₂RhSi₃ (RE = Y, La → Er), RERhSi (Y, La, Gd → Er), REIrSi (RE = La, Ce, Nd), RERhSi₂ and REIrSi₂ (RE = La → Gd). The RE₂RhSi₃ compounds crystallize with a new structural type, the other ones are isostructural with already known silicides or borides. Some of the silicides studied whose rare earths are diamagnetic (Y, La) show superconducting transitions above 1.6 K. They have been compared with other superconducting ternary borides, silicides, germanides and phosphides containing rare earths and noble metals. Except the phases with Y and La which are diamagnetic or show Pauli paramagnetism, the other materials order magnetically at low temperature. The onset of magnetic transitions vs. field has been observed for some compounds below 20 kOe at 4.2 K.     

Magnetic properties of Pd doped with Fe: Intermediate between ferromagnetism and spinglass behavior

The electrical impedance, the ac susceptibility, and the ad magnetization of Pd doped with Fe, whose concentration is between the one for ferromagnetic order and spinglass behaviour, were investigated in the temperature range from 2 mK to 4K and at 0.3T H 2 mT. This Fe concentration is between the one for spin glass freezing and the one for ferromagnetic order. With the ac susceptibility and the dc magnetization data, we can exclude a ferromagnetic transition or a reentrant magnetic phase transition. The ac susceptibility, measured directly as well as extracted from the imaginary part of the ac impedance, shows magnetic clustering followed by spin glass (spincluster glass) freezing at 50 mK. The resistivity, obtained from the real part of the ac impedance, exhibits a very complicated temperature dependence which can be understood in terms of spin fluctuations, magnetic clustering, and electron-magnon scattering inside of the magnetic clusters.     

Electrical properties of poly(n-butylamino) (di-allylamino) phosphazene

A new organic–inorganic hybrid polymer, poly(n-butylamino) (di-allylamino) phosphazene, is synthesized and electrical properties of the polymer are reported. From the results of Fourier transform infrared (FTIR), 1H-nuclear magnetic resonance (NMR) and 31P-NMR measurements, it was confirmed that the synthesized polymer was poly(n-butylamino) (di-allylamino) phosphazene. From an Arrhenius plot of d.c. conduction it was found that experimental points fit to two straight lines, that the discontinuous point could be the glass transition (Tg=268.9 K) and that the activation energies are 0.74 and 1.5 eV at temperatures higher and lower than Tg, respectively. Dielectric constant and dielectric loss factors were measured over the temperature range from –20°C to 70°C with frequency 100 Hz100 kHz, and a dielectric loss contour was obtained. A relaxation process with the activation energy of 1.44 eV was found from the dielectric loss contour, which can be attributed to relaxation. A comparison was made between the present results and those of other phosphazene polymers. Because the polymer was non-flammable and shows high resistance and low dielectric constant, it could be used as an insulator in the field of electronics. © 1998 Kluwer Academic Publishers     

Electrical properties of iron (III) molybdate

Electrical transport properties, i.e. a.c. and d.c. electrical conductivities, thermoelectric power and dielectric constant, of Fe₂(MoO₄)₃ have been measured in the temperature range 300 to 1000 K on pressed pellets of a polycrystalline sample, using the two electrode method. Iron (III) molybdate has been found to be a p-type semiconductor with an energy gap of 3.1 eV. Intrinsic conduction occurs at 750 K and the activation energies below and above 750 K are 0.51 and 1.55 eV, respectively. The thermoelectric power increases up to 750 K and after that it decreases with increasing temperature. The dielectric constant increases with temperature over the entire temperature range measured except 650 to 750 K, where it has a constant value.[/p]     

Electrical transport properties of iron (II) molybdate

Electrical conductivity, thermoelectric power and static dielectric constant of iron (II) molybdate have been measured in the temperature range 300 to 1000 K on pressed pellets of polycrystalline sample. It has been found that FeMoO₄ is a p-type semiconductor with energy gap 4.1 eV. Different conduction mechanisms have been found below and above 700 K. Below 700 K conduction is due to a small polaron hopping mechanism and above 700 K conduction is due to large polarons as well as normal band conduction mechanism. Activation energy W, ₀ (T) and charge carrier mobility have been estimated in the two temperature ranges 300 to 700 K and 700 to 1000 K. Dielectric constant increases slowly with temperature up to 700 K and above 700 K, it increases exponentially with temperature.     

PZT 95/5-2Nb铁电陶瓷脉冲换能电输出

讨论了PZT 95/5-2Nb铁电陶瓷在冲击波压缩下的释放电性能,并利用PZT 95/5-2Nb铁电陶瓷设计了三种脉冲电源,分别实现了恒定电流、台阶电流和恒定电压等不同条件的电能输出.实验结果表明,PZT 95/5-2Nb铁电陶瓷可适用于多种性能的脉冲能源,具有电流输出幅值和波形易于控制,电流脉冲上升前沿陡,电源体积小等特点,具有广阔的应用前景.     

Electrical properties of electroplated Cu(Ag) thin films

To increase the electromigration resistance of copper interconnects copper alloy systems are of interest. In the present paper electrical properties of Cu(Ag) films will be discussed with respect to heat treatment and in comparison to copper and other alloy systems. The investigations show that the electrical resistivity of Cu(Ag) films is very low in comparison to other copper alloy systems. Up to an alloy content of about 2 at.% Ag the International Technology Roadmap for Semiconductors criterion of 2.2 μΩcm (scattering by geometrical constraints neglected) can be fulfilled after heat treatment. The various components of the electrical resistivity will be discussed in detail. The investigations show that grain growth and the redistribution of silver and impurities dominate the electrical resistivity evolution.     

Electrical properties of electrodeposited zinc selenide (ZnSe) nanowires

In this work, zinc selenide (ZnSe) nanowires were fabricated on indium-tin oxide coated glass substrate via template-assisted electrodeposition method from an electrolytic solution of zinc (II) sulphate (ZnSO₄·7H₂O) and selenium dioxide (SeO₂). ZnSe nanowires of diameter 100 nm have been fabricated using polycarbonate track-etch membrane. Electrodeposition was done at 30 °C temperature and the length of the nanowires was controlled by adjusting the deposition time. Both morphological and electrical characteristics were studied. Sample characterization was done using scanning electron microscope and X-ray diffraction. I–V measurements reveal that the ZnSe nanowires have non-linear behavior like Schottky diode characteristics. Further, the ZnSe nanowires were used in astable multivibrator which acts as capacitor to give conventional output behavior. The temperature dependent capacitive properties of ZnSe nanowires reveal that ZnSe nanowire can be used as temperature sensor.     

Mg95Ni5-30wt%La0.7Mg0.3Ni2.8Co0.5复合物的吸放氢性能研究

先采用氢化燃烧合成法制备Mg95Ni5,然后将氢化燃烧合成产物与30%(质量分数)La0.7Mg0.3Ni2.8Co0.5合金进行机械球磨复合,球磨时间分别为5、10、15和20h;将Mg95Ni5的氢化燃烧合成产物直接球磨10h用于对比研究.采用X射线衍射仪、扫描电镜、能谱仪及气体反应控制器研究了材料的相组成、微观形貌、颗粒化学成分以及吸放氢性能.研究表明,球磨10h的Mg95Ni5/La0.7Mg0.3Ni2.8Co0.5复合物具有最佳的吸放氢性能,在373K,50s内基本达到饱和吸氢量3.78%(质量分数);在523K,1800s内放氢量为3.83%(质量分数);其起始放氢温度为425K,与Mg95Ni5相比降低了35K,吸放氢性能的改善与复合物的组织结构密切相关.此外,La0.7Mg0.36Ni2.8Co0.5的加入改善了复合物的放氢动力学性能.     

Fe(CO)5 molecule as a nanostructed system

Solid iron pentacarbonyl, Fe(CO)₅ in form of bulk and as physisorbed islands on graphite show similar dynamic properties in spite of their different crystal structures. The discrete behavior of the Debye-Waller factor and dielectric constant suggest that the Fe(CO)₅ molecule forms a nanostructured system, practically independent of its immediate neighborhood.