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Electrical Resistivity (electrical + resistivity)
Terms modified by Electrical Resistivity Selected AbstractsElectrolytic Synthesis of Al-Doped ZnO Nanopowders With Low Electrical ResistivityJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2010Takeshi Takaki Al-doped ZnO (AZO) nanopowders with different Al content were fabricated by a galvanostatic electrolytic method. The electrical resistivities were measured by a cell method, which reached its minimum (28 ,·cm) at 0.93 at.% of Al with its grain size of ,30 nm. Microstructures of powders were characterized by X-ray diffraction and transmission electron microscopy (TEM), which showed a decrease in grain size with the increase of Al content. In addition, the distributions of Al and the chemical bonding nature of Al atoms were examined by STEM-EDS and by X-ray photoelectron spectra, respectively, which suggested the substituational incorporation of Al atom into the ZnO lattice. Absorption properties were investigated for wavelength ranging from 250 to 2500 nm, which showed that the film coated with AZO nanopowders exhibited a rapid decrease in transmittance below 370 nm to ,0% and beyond 1250 nm to ,40% (at 2000 nm). [source] Electrical Resistivity and Phase Transformation in SteelsMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 1 2003O. N. Mohanty Elektrischer Widerstand; Phasenumwandlung; Magnetische Eigenschaften Abstract Changes in electrical resistance accompanying transformations in steels with magnetic change (e.g. , , martensite/bainite) and without magnetic change (e.g. , , ,, above Curie temperature) have been examined; the former class affects the resistivity the latter does not. Next, while the efficacy of electrical resistivity measurement in capturing the well-known features of austenite stabilization (e.g. over , ageing, reversibility, and influence of prior martensite amount and so on) in high carbon steels has been reported in an earlier publication, new features (e.g. increase in resistance -increase at very low temperatures, change in temperature co-efficient of resistivity in the stabilized material etc.) are highlighted here. Finally, the work shows that a quantitative estimate of precipitation in the copper bearing, age-hardenable HSLA-100 steel during tempering can be done by continuous electrical resistivity measurement. These data also allow an in-depth kinetic analysis using the Johnson-Mehl-Avrami equation. Zusammenhang zwischen elektrischem Widerstand und Phasenumwandlungen in Stählen Änderungen des elektrischen Widerstands wurden im Zusammenhang mit Phasenumwandlungen, die zu Änderungen der magnetischen Eigenschaften führen (z.B. , , Martensit/Bainit), und solchen, die keine Änderungen der magnetischen Eigenschaften bewirken (z.B. , , , oberhalb der Curie-Temperatur), untersucht. Während sich die erste Umwandlungsart auswirkt, gilt dies für die andere nicht. Während über die Empfindlichkeit von Widerstandsmessungen zur Erfassung der Austenitstabilisierung (z.B. Überalterung, Umkehrbarkeit, Einfluß des vorher vorhandenen Martensitanteils, usw.) in übereutektoiden Stählen in einer früheren Veröffentlichung berichtet wurde, wird im zweiten Teil der hier vorgelegten Veröffentlichung auf neuerdings erfassbare Merkmale (z.B. der Anstieg des Widerstands bei sehr niedrigen Temperaturen, die Änderung der Temperaturabhängigkeit des Widerstands im stabilisierten Material, usw.) eingegangen. Schließlich zeigt die Arbeit, daß durch kontinuierliche Widerstandsmessungen während des Anlassens eine quantitative Abschätzung der Ausscheidungsgehalte im kupferhaltigen, ausscheidungsverfestigenden HSLA-100-Stahl erfolgen kann. Die Daten hierzu erlauben zudem eine vertiefte kinetische Analyse auf Basis der Johnson-Mehl-Avrami-Gleichung. [source] MOCVD of Platinum Films from (CH3)3CH3CpPt and Pt(acac)2: Nanostructure, Conformality, and Electrical Resistivity,CHEMICAL VAPOR DEPOSITION, Issue 4 2003J. Goswami Abstract A potentially manufacturable liquid-source MOCVD process was applied to deposit platinum (Pt) films (12,140,nm) on thermally oxidized Si substrates. The deposition of Pt films was carried out at a substrate temperature of 350,°C by oxygen-assisted pyrolysis of complex precursors in a low-pressure, hot-wall reactor. The effects of two different metal,organic precursors, a) trimethyl methyl cyclopentadienyl platinum [(CH3)3CH3CpPt], and b) platinum acetylacetonate [Pt(acac)2], on the properties of Pt films were studied. Although the polycrystalline Pt films deposited from Pt(acac)2 exhibited a preferred (111) orientation with a X-ray intensity ratio of I(111)/I(200),=,40, the films deposited from (CH3)3CH3CpPt were highly (111) oriented with I(111)/I(200),=,270. The following properties were typical of Pt films from Pt(acac)2 as compared to Pt films from (CH3)3CH3CpPt: finer grain size (25,nm vs. 50,nm), smaller root mean square (rms) surface roughness (5,nm vs. 15,nm), and better step coverage (95,% vs. 35,%). These experimental findings indicated that growth of Pt films from Pt(acac)2 occurred under the kinetically-limited regime, whereas the deposition of Pt from (CH3)3CH3CpPt was limited by the mass transport rate. Additionally, the temperature (4.2,293,K) dependence of the electrical resistivities (,) of Pt films was measured and the electron mean free paths were estimated. It was observed that ,(T) deviated from Matthiessen's rule. [source] Preparation and characterization of powders and crystals of Vn-xTixO2n-1 Magneli oxidesCRYSTAL RESEARCH AND TECHNOLOGY, Issue 10-11 2005D. Calestani Abstract Vn-xTixO2n-1 Magnéli phases have been synthesized under vacuum in powder form (n = 4, 0 , x , 0.4) and crystals (n = 4 and 5, x = 0.5 and 1.4, respectively), grown by chemical vapour transport in closed ampoules. TeCl4 and NH4Cl were used as transporting agents. Needle-shaped crystals as long as 200-300 micrometers or 2-3 mm were obtained when in presence of NH4Cl or TeCl4, respectively. The powder and crystal structures were examined by X-ray diffraction and the transport and magnetic characteristics were measured.. The powders resulted to be single-phase and the relevant composition was assumed to be equal to the nominal one. The overall stoichiometry of compounds, n, was determined from single crystal X-ray diffraction data. The Ti content, x, was deduced from the elementary cell volume, by applying the Végard law. Crystals were mainly untwinned and of good quality. The elementary cell of both, powders and crystals, was triclinic (P-1) and did not change with doping. DC electrical resistivity of the crystals was measured in a four-points (van der Pauw) configuration. DC magnetic susceptibility of the powders was measured in a SQUID magnetometer. The Ti doping was found to progressively smooth and finally to suppress the magnetic transitions occurring in the V4O7. The metal-insulator transitions observed in V4O7 and V5O9, at around 235 and 125 K respectively, were not observed in the doped crystals, thus indicating some significant change of the electronic structure of the V oxides. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Sc3AlN , A New PerovskiteEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2008Carina Höglund Abstract Sc3AlN with perovskite structure has been synthesized as the first ternary phase in the Sc,Al,N system. Magnetron sputter epitaxy at 650 °C was used to grow single-crystal, stoichiometric Sc3AlN(111) thin films onto MgO(111) substrates with ScN(111) seed layers as shown by elastic recoil detection analysis, X-ray diffraction, and transmission electron microscopy. The Sc3AlN phase has a lattice parameter of 4.40 Å, which is in good agreement with the theoretically predicted 4.42 Å. Comparisons of total formation energies show that Sc3AlN is thermodynamically stable with respect to all known binary compounds. Sc3AlN(111) films of 1.75 µm thickness exhibit a nanoindentation hardness of 14.2 GPa, an elastic modulus of 249 GPa, and a room-temperature electrical resistivity of 41.2 µ, cm. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Study of the Defects in Sintered SnO2 by High-Resolution Transmission Electron Microscopy and CathodoluminescenceEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2007David Maestre Abstract The defect structure of sintered SnO2 was investigated by high-resolution transmission electron microscopy (HRTEM), cathodoluminescence (CL), and electrical measurements. HRTEM shows the presence of the SnO phase in the sintered samples as well as twinning, stacking faults, and disordered intergrowths. The sintered samples annealed under an oxygen atmosphere show changes in the defect structure and in the CL spectra. In particular, the intensity of a CL band at 1.94 eV, related to oxygen vacancies, decreased as the electrical resistivity increased. The results are discussed by considering the presence of stoichiometric defects such as oxygen vacancies and Sn interstitials in the final structure and their evolution during the annealing process under an oxygen atmosphere. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Natural Aging in Al-Mg-Si Alloys , A Process of Unexpected Complexity,ADVANCED ENGINEERING MATERIALS, Issue 7 2010John Banhart The natural aging behavior of pure ternary Al-Mg-Si alloys is investigated by measuring hardness, electrical resistivity and positron lifetime, as well as carrying out thermal analysis and atom probe microscopy. It is found that several distinct temporal stages of natural aging can be distinguished in which one of these quantities shows a characteristic behavior and that these times coincide for many of these measurements. The rate of change in the measured data is correlated with proposed solute dynamics during natural aging for both aging that takes place prior to artificial aging (natural pre-aging) and after artificial underaging (natural secondary aging) heat treatments. Controlling factors for solute dynamics are discussed. [source] Characterization of Ti-Ta Alloys Synthesized by Cold Crucible Levitation Melting,ADVANCED ENGINEERING MATERIALS, Issue 8 2008D.-M. Gordin Ti-Ta alloys are potentially interesting for many applications including chemistry industries, marine environment and biomedical devices. In this study, the Ti-Ta alloys were synthesized by cold crucible levitation melting (CCLM) in the whole range of composition. The different microstructures were characterized by X-ray diffraction and optical microscopy, the ,-transus was detected by electrical resistivity, the mechanical properties were evaluated by compression tests and microhardness measurements and the electrochemical behavior was carried out in Ringer's solution. [source] Relationship between Condition of Deposition and Properties of W-Ti-N Thin Films Prepared by Reactive Magnetron Sputtering,ADVANCED ENGINEERING MATERIALS, Issue 3 2006V. Kuchuk A correlation between the film properties of nitrides, oxides etc., and their structure, is of fundamental importance , not only for thin solid films physics but also for practical applications. The structure of the films depends on deposition methods and their parameters. The relationship between properties (chemical and phase compositions, surface morphology, and electrical resistivity) and nitrogen partial pressure of reactive magnetron sputtered W-Ti-N thin films has been discussed here in detail. [source] Traversing the Metal-Insulator Transition in a Zintl Phase: Rational Enhancement of Thermoelectric Efficiency in Yb14Mn1,xAlxSb11,ADVANCED FUNCTIONAL MATERIALS, Issue 18 2008Eric S. Toberer Abstract For high temperature thermoelectric applications, Yb14MnSb11 has a maximum thermoelectric figure of merit (zT) of ,1.0 at 1273,K. Such a high zT is found despite a carrier concentration that is higher than typical thermoelectric materials. Here, we reduce the carrier concentration with the discovery of a continuous transition between metallic Yb14MnSb11 and semiconducting Yb14AlSb11. Yb14Mn1-xAlxSb11 forms a solid solution where the free carrier concentration gradually changes as expected from the Zintl valence formalism. Throughout this transition the electronic properties are found to obey a rigid band model with a band gap of 0.5,eV and an effective mass of 3 me. As the carrier concentration decreases, an increase in the Seebeck coefficient is observed at the expense of an increased electrical resistivity. At the optimum carrier concentration, a maximum zT of 1.3 at 1223,K is obtained, which is more than twice that of the state-of-the-art Si0.8Ge0.2 flown by NASA. [source] Reconstruction of the Water Table from Self-Potential Data: A Bayesian ApproachGROUND WATER, Issue 2 2009A. Jardani Ground water flow associated with pumping and injection tests generates self-potential signals that can be measured at the ground surface and used to estimate the pattern of ground water flow at depth. We propose an inversion of the self-potential signals that accounts for the heterogeneous nature of the aquifer and a relationship between the electrical resistivity and the streaming current coupling coefficient. We recast the inversion of the self-potential data into a Bayesian framework. Synthetic tests are performed showing the advantage in using self-potential signals in addition to in situ measurements of the potentiometric levels to reconstruct the shape of the water table. This methodology is applied to a new data set from a series of coordinated hydraulic tomography, self-potential, and electrical resistivity tomography experiments performed at the Boise Hydrogeophysical Research Site, Idaho. In particular, we examine one of the dipole hydraulic tests and its reciprocal to show the sensitivity of the self-potential signals to variations of the potentiometric levels under steady-state conditions. However, because of the high pumping rate, the response was also influenced by the Reynolds number, especially near the pumping well for a given test. Ground water flow in the inertial laminar flow regime is responsible for nonlinearity that is not yet accounted for in self-potential tomography. Numerical modeling addresses the sensitivity of the self-potential response to this problem. [source] Tracing solute infiltration using a combined method of dye tracer test and electrical resistivity tomography in an undisturbed forest soil profileHYDROLOGICAL PROCESSES, Issue 21 2010Jae Gon Kim Abstract An accurate prediction of solute infiltration in a soil profile is important in the area of environmental science, groundwater and civil engineering. We examined the infiltration pattern and monitored the infiltration process using a combined method of dye tracer test and electrical resistivity tomography (ERT) in an undisturbed field soil (1 m × 1 m). A homogeneous matrix flow was observed in the surface soil (A horizon), but a preferential flow along macropores and residual rock structure was the dominant infiltration pattern in the subsurface soil. Saturated interflow along the slopping boundaries of A and C1 horizons and of an upper sandy layer and a lower thin clay layer in the C horizon was also observed. The result of ERT showed that matrix flow started first in A horizon and then the infiltration was followed by the preferential flows along the sloping interfaces and macropores. The ERT did not show as much detail as the dye-stained image for the preferential flow. However, the area with the higher staining density where preferential flow was dominant showed a relatively lower electrical resistivity. The result of this study indicates that ERT can be applied for the monitoring of solute transportation in the vadose zone. Copyright © 2010 John Wiley & Sons, Ltd. [source] Nonuniform Nanowire Doping Profiles Revealed by Quantitative Scanning Photocurrent MicroscopyADVANCED MATERIALS, Issue 30 2009Jonathan E. Allen Scanning photocurrent microscopy (SPCM) is used in semiconductor nanowire devices to establish quantitative potential profiles correlated with nonuniformities in electrical resistivity. Surface doping leads to a nonuniform axial photocurrent (a). Surface etching improves the uniformity of the local photocurrent (b) and reduces the radial and axial carrier concentration gradients (c, blue curve after etching). [source] Synergistic effects of carbon fillers on shielding effectiveness in conductive nylon 6,6- and polycarbonate-based resinsADVANCES IN POLYMER TECHNOLOGY, Issue 2 2003Quinton J. Krueger Abstract Electrically conductive resins can be made by adding electrically conductive fillers to typically insulating polymers. Resins with an electrical resistivity of approximately 100 , cm or less can be used for electromagnetic and radio frequency interference shielding applications. This research focused on performing compounding runs followed by injection molding and shielding effectiveness (SE) testing of carbon filled nylon 6,6- and polycarbonate-based resins. The three carbon fillers investigated included an electrically conductive carbon black, synthetic graphite particles, and a milled pitch-based carbon fiber. For each polymer, conductive resins were produced and tested that contained varying amounts of these single carbon fillers. In addition, combinations of fillers were investigated by conducting a full 23 factorial design and a complete replicate in each polymer. The objective of this study was to determine the effects and interactions of each filler on the SE properties of the conductive resins. Carbon black caused the largest increase in SE. Also, each single filler and each two filler interaction caused a statistically significant increase in SE. © 2003 Wiley Periodicals, Inc. Adv Polym Techn 22: 96,111, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.10040 [source] Polyaniline-multiwalled carbon nanotube composites: Characterization by WAXS and TGAJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008T. Jeevananda Abstract Polyaniline/carboxylated multi-walled carbon nanotube (PAni/c-MWNT) nanocomposites have been synthesized by micellar aided emulsion polymerization with various c-MWNTs compositions, viz., 0.5, 1, 5, and 10 wt %. The microcrystalline parameters such as the nanocrystal size (,N,), lattice strain (g), interplanar distance (dhkl), width of the crystallite size distribution, surface weighted crystal size (Ds), and volume of the ordered regions were calculated from the X-ray data by using two mathematical models, namely the Exponential distribution and Reinhold distribution methods. The effects of heat ageing on the microcrystalline parameters of the PAni/c-MWNT nanocomposites were also studied and the results are correlated. The thermal stability and electrical resistivity of the PAni/c-MWNT nanocomposites were examined with thermogravimetric analysis (TGA) and a conventional two-probe method. The TGA data indicate that the thermal stability of the nanocomposites improved after the incorporation of c-MWNTs. The influence of temperature on the resistivity of the nanocomposites was also measured. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008 [source] Nonlinear surface electrical resistivity of graphite,polyurethane composite filmsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Ganesh K. Kannarpady Abstract In this article, we study the surface resistivity of graphite,polyurethane composites using voltage,current characteristics. The evolution of the percolation network of graphite in polyurethane is qualitatively studied using optical micrographs. As expected, the surface resistivity decreases as a function of graphite concentration. In particular, the surface resistivity of the 69% graphite,polyurethane composite is about four orders of magnitude lower than the surface resistivity of the 27% graphite,polyurethane composite. The electrical resistivity of the composite is found to be highly nonlinear with respect to an increasing voltage at a low graphite weight fraction. On the other hand, the nonlinearity is significantly milder at higher weight fractions. The reasons behind the nonlinearity are discussed. Very preliminary studies indicate that very low weight fractions of single wall carbon nanotubes (e.g. 2.5%) are sufficient to generate electrical conductivities comparable to much higher loading fractions (, 60% and higher) of the heavier graphite particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] High-Energy Density Capacitors Utilizing 0.7 BaTiO3,0.3 BiScO3 CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2009Hideki Ogihara A high, temperature-stable dielectric constant (,1000 from 0° to 300°C) coupled with a high electrical resistivity (,1012,·cm at 250°C) make 0.7 BaTiO3,0.3 BiScO3 ceramics an attractive candidate for high-energy density capacitors operating at elevated temperatures. Single dielectric layer capacitors were prepared to confirm the feasibility of BaTiO3,BiScO3 for this application. It was found that an energy density of about 6.1 J/cm3 at a field of 73 kV/mm could be achieved at room temperature, which is superior to typical commercial X7R capacitors. Moreover, the high-energy density values were retained to 300°C. This suggests that BaTiO3,BiScO3 ceramics have some advantages compared with conventional capacitor materials for high-temperature energy storage, and with further improvements in microstructure and composition, could provide realistic solutions for power electronic capacitors. [source] High Q Microwave Dielectric Ceramics in (Ni1,x Znx)Nb2O6 SystemJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2009Sandeep Butee (Ni1,xZnx)Nb2O6, 0,x,1.0, ceramics with >97% density were prepared by a conventional solid-state reaction, followed by sintering at 1200°,1300°C (depending on the value of x). The XRD patterns of the sintered samples (0,x,1.0) revealed single-phase formation with a columbite (Pbcn) structure. The unit cell volume slightly increased with increasing Zn content (x). All the compositions showed high electrical resistivity (,dc=1.6±0.3 × 1011,·cm). The microwave (4,5 GHz) dielectric properties of (Ni1,xZnx)Nb2O6 ceramics exhibited a significant dependence on the Zn content and to some extent on the morphology of the grains. As x was increased from 0 to 1, the average grain size monotonically increased from 7.6 to 21.2 ,m and the microwave dielectric constant (,,r) increased from 23.6 to 26.1, while the quality factors (Qu×f) increased from 18 900 to 103 730 GHz and the temperature coefficient of resonant frequency (,f) increased from ,62 to ,73 ppm/°C. In the present work, we report the highest observed values of Qu×f=103 730 GHz, and ,,r=26.1 for the ZnNb2O6 -sintered ceramics. [source] Effect of A Site Substitution on the Properties of CaBi2Nb2O9 Ferroelectric CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2008Xiaodong Zhang The effect of A-site substitution on the piezoelectric coefficient, high-temperature dc resistivity, and thermal depoling behavior of Aurivillius phase CaBi2Nb2O9 ferroelectric ceramics was investigated. Ceramics with the general formula of Ca1,xMxBi2Nb2O9, where M=Na, (Na,Ce), (Na,La), and La, were prepared by conventional solid-state sintering. All the ceramics were single-phase ferroelectrics with high Curie points (,900°C). The doped ceramics, Ca0.9Na0.1Bi2Nb2O9, Ca0.9(NaLa)0.1Bi2Nb2O9, Ca0.95La0.05Bi2Nb2O9, and Ca0.9La0.1Bi2Nb2O9, had improved resistance to thermal depoling compared with Ca2Bi2Nb2O9 and were stable up to 800°C. The donor dopants increased the dc electrical resistivity, while the acceptor dopants decreased it. The donor-doped Ca0.95La0.05Bi2Nb2O9 had a higher piezoelectric constant (d33=12.8 pC/N) compared with CaBi2Nb2O9 (d33=5.8 pC/N), and its electrical resistivity was higher than 106,·cm at 600°C. These properties suggest that doped CaBi2Nb2O9 ceramics might be good candidates for high-temperature piezoelectric applications. [source] Effects of Individual Layer Thickness on the Microstructure and Optoelectronic Properties of Sol,Gel-Derived Zinc Oxide Thin FilmsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2008Noureddine Bel Hadj Tahar Zinc oxide (ZnO) thin films were prepared under different conditions on glass substrates using a sol,gel process. The microstructure of ZnO films was investigated by means of diffraction analysis, and plan-view and cross-sectional scanning electron microscopy. It was found that the preparation conditions strongly affected the structure and the optoelectronic properties of the films. A structural evolution in morphology from spherical to columnar growth was observed. The crystallinity of the films was improved and columnar film growth became more dominant as the zinc concentration and the substrate withdrawal speed decreased. The individual layer thickness for layer-by-layer homoepitaxy growth that resulted in columnar grains was <20 nm. The grain columns are grown through the entire film with a nearly unchanged lateral dimension through the full film thickness. The columnar ZnO grains are c -axis oriented perpendicular to the interface and possess a polycrystalline structure. Optical transmittance up to 90% in the visible range and electrical resistivity as low as 6.8 × 10,3·,·cm were obtained under optimal deposition conditions. [source] Synthesis and Electrical Properties of Stabilized Manganese Dioxide (,-MnO2) Thin-Film ElectrodesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2008Do-Kyun Kwon Manganese dioxide (,-MnO2) thin films have been explored as a cathode material for reliable glass capacitors. Conducting ,-MnO2 thin films were deposited on a borosilicate glass substrate by a chemical solution deposition technique. High carbon activities originated from manganese acetate precursor, (Mn(C2H3O2)2·4H2O) and acetic acid solvent (C2H4O2), which substantially reduced MnO2 phase stability, and resulted in Mn2O3 formation at pyrolysis temperature in air. The ,-MnO2 structure was stabilized by Ba2+ insertion into a (2 × 2) oxygen tunnel frame to form a hollandite structure. With 15,20 mol% Ba addition, a conducting ,-MnO2 thin film was obtained after annealing at 600,650°C, exhibiting low electrical resistivity (,1 ,·cm), which enables application as a cathode material for capacitors. The hollandite ,-MnO2 phase was stable at 850°C, and thermally reduced to the insulating bixbyte (Mn2O3) phase after annealing at 900°C. The phase transition temperature of Ba containing ,-MnO2 was substantially higher than the reported transition temperature for pure MnO2 (,500°C). [source] Enhancement of Tc(0) by Substitution of Gallium in the Bismuth-Based High- Tc Superconducting MaterialJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2008Muhammad Javed Iqbal We report the enhancement of the zero resistivity Tc(0) by 5.5 K i.e. from 104 to 109.5 K by substitution of gallium 1.34% of copper in the bismuth 2223 compound. A series of Ga-containing compounds Bi2Pb0.4Sr2Ca2Cu3,xGaxOy (x=0.00, 0.02, 0.04, 0.06, and 0.08) are synthesized by the solid-state reaction method. The samples are characterized by measurements of their dc electrical resistivity and ac magnetic susceptibility and by the powder X-ray diffraction analysis. It is noted that the high- Tc (2223) phase increases from 57.55% in an undoped sample to 92.99% in samples containing a low concentration of gallium i.e. x,0.04. [source] Crystal Structure and Characterization of Pure and Ag-Doped (La1,xYx)2Ba2CaCu5Oz (0,x,0.5) SuperconductorsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2007Pramoda Kumar Nayak Pure and 5 wt% of Ag-doped (La1,xYx)2Ba2CaCu5Oz superconducting compounds for x=0,0.5 have been prepared. Analysis of X-ray diffraction patterns shows that the samples are essentially in the single-phase form and they could be refined using the P4/mmm space group in a tetragonal cell. The typical lattice parameters are found to be a=b=3.879 Å, c=11.646 Å for x=0 and a=b=3.856 Å, c=11.576 Å for x=0.5 samples. The detailed crystal structure parameters are presented. The average grain size values from scanning electron microscope images are found to be in the order of 1,3 ,m. Temperature variations of ac susceptibility and electrical resistivity have been measured. Superconducting transitions with diamagnetic Tc ranging from 60 to 75 K have been observed, with the maximum Tc for the x=0.25 sample. Ag-doped samples exhibit improved inter-granular coupling and homogeneous oxygenation. [source] Phase diagram of the NdFe1,xRhx AsO superconductorPHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 3-4 2010H. Y. Shi Abstract Polycrystalline samples with a nominal composition of NdFe1,xRhx AsO (0 , x , 0.25) were synthesized using a solid state reaction method. Bulk superconductivity with a maximum TC = 13 K is observed in the x = 0.1 sample. A temperature,composition phase diagram is established for the NdFe1,xRhx AsO system based on the electrical resistivity and magnetization measurements. A first-order-like transition from an antiferromagnetic state to the superconducting state at a critical Rh-doping point xC , 0.045 is observed in the present phase diagram. The value for the upper critical field ,0Hc2(0) is estimated to be about 26 T for the x = 0.10 sample by using the Werthamer,Helfand,Hohenberg theory. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Synthesis and thermoelectric properties of YbSb2Te4PHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 6 2007Amado S. Guloy Abstract The study of the ternary phase diagram Yb,Sb,Te has led to the synthesis of YbSb2Te4 as a pure phase by way of high energy ball milling followed by annealing, whereas typical high temperature powder metallurgy leads to multiphase sample with impurities of the very stable YbTe. The Hall mobility, Seebeck coefficient, electrical resistivity and thermal conductivity of the layered compound YbSb2Te4 were measured in the range of 20,550 °C. The thermoelectric figure of merit peaks at 525 K and reaches 0.5. Of particular interest is the very low lattice thermal conductivity (as low as a glass) which makes YbSb2Te4 and related compounds promising thermoelectric materials. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Optical, structural, and electrical properties of Cu2O thin filmsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2010Ferid Chaffar Akkari Abstract Glancing-angle deposition (GLAD) was used in this work to grow transparent oxide Cu2O thin films by annealing in air at 185,°C of copper films deposited firstly by this method onto glass substrates. The annealing temperature of 185,°C corresponds to the optimal temperature that corresponds to the formation of Cu2O phase. The copper was sculptured into a zigzag shape, which present case (i) one column with inclined angle ,, case (ii) two columns with inclined angles , and ,,, and case (iii) three copper inclined columns with inclined angles ,, ,,, and , where , is the deposition angle between the incident flux and the substrate surface normal. The films after annealing have thicknesses of 165, 185, and 265,nm for cases (i), (ii), and (iii), respectively. The air-annealed copper films were characterized for their structural, surface morphological; electrical and optical properties by using X-ray diffraction (XRD), scanning electron microscopy (SEM), electrical resistivity, and optical (transmittance and reflectance) measurement techniques. Optical studies show a direct allowed transition around 2.5,eV for the three cases. High absorptions coefficients in the range 2,×,105,3.7,×,106,cm,1 were found for photon energies higher than 2.7,eV. The Cu2O films exhibit in cases (i) and (ii) p-type conductivity but in case (iii) the Cu2O films exhibit n-type conductivity. [source] Unique structure of ZnO films deposited by chemical bath depositionPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2009Dewei Chu Abstract The unique structure of ZnO films obtained from aqueous solution method was investigated. Scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) analyses indicate that unique morphology and structure of the region where precipitation on the substrate may occur in parallel with other regions. This is accompanied by a decrease of the electrical resistivity in the absorbed region. A possible mechanism for the resistivity transformation was discussed. [source] Hole,polar phonon interaction scattering mobility in chain structured TlSe0.75S0.25 crystalsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2009A. F. Qasrawi Abstract In this study, the electrical resistivity, charge carriers density and Hall mobility of chain structured TlSe0.75S0.25 crystal have been measured and analyzed to establish the dominant scattering mechanism in crystal. The data analyses have shown that this crystal exhibits an extrinsic p-type conduction. The temperature-dependent dark electrical resistivity analysis reflected the existence of three energy levels located at 280 meV, 68 meV and 48 meV. The temperature dependence of carrier density was analyzed by using the single donor,single acceptor model. The carrier concentration data were best reproduced assuming the existence of an acceptor impurity level being located at 68 meV consistent with that observed from resistivity measurement. The model allowed the determination of the hole effective mass and the acceptor,donor concentration difference as 0.44m0 and 2.2 × 1012 cm,3, respectively. The Hall mobility of the TlSe0.75S0.25 crystal is found to be limited by the scattering of charged carriers over the (chain) boundaries and the scattering of hole,polar phonon interactions above and below 300 K, respectively. The value of the energy barrier height at the chain boundaries was found to be 261 meV. The polar phonon scattering mobility revealed the high-frequency and static dielectric constants of 13.6 and 15.0, respectively. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Spectroscopic ellipsometry study of thin diffusion barriers of TaN and Ta for Cu interconnects in integrated circuitsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2008S. Rudra Abstract The objective of this work is to study the optical and electrical properties of tantalum nitride and tantalum barrier thin films used against copper diffusion in Si in integrated circuits using spectroscopic ellipsometry in the VUV and UV,visible range. Single layers of tantalum nitride and bilayer films of Ta/TaN were produced by reactive magnetron sputtering on Si(100) substrates covered with a native oxide layer. Ellipsometric measurements were performed in the energy range from 0.73,8.7 eV and the dielectric functions were simulated using Drude,Lorentz model and effective medium approximation (EMA) in order to obtain information regarding film thickness, film composition, free carrier plasma energy, mean relaxation time and electrical resistivity. The film thickness clearly affects the electrical resistivity and the electron mean free path. It was observed that for films of Ta on TaN even after maintaining the deposition condition suitable for the ,-phase of Ta, it turned out to be a mixture of ,- and ,-phases with higher contribution of the ,-phase. It is shown that even a very small intermixture of two different phases of Ta can be determined accurately using ellipsometry. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Crystallization study of amorphous Pd43Ni10Cu27P20 alloy by internal friction measurementPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 10 2007K. W. Yang Abstract We have successfully measured the internal friction and electrical resistivity of Pd43Ni10Cu27P20 bulk metallic glass during a constant heating process. The results of electrical resistivity suggest that the position of the internal friction peak is the onset temperature of crystallization. The dependence of internal friction on frequencies show both linear and nonlinear relations. The internal friction at 623 K in the supercooled liquid region decreases monotonously with the increase of annealing time, indicating structural relaxation and subsequent crystallization occurs during isothermal annealing near the crystallization temperature. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||||||||||||||||||||||||||