Electrical conductivity and transition temperature of NbN thin films

Niobium nitride thin films are grown using reactive RF sputtering technique for four different partial nitrogen pressures in argon atmosphere. The superconducting transition temperature of the films has been measured. The films exhibit a negative temperature coefficient of resistivity. The electrical characterization of the films has been carried out and the conductivity measured between room temperature and liquid nitrogen temperature. This is fitted usingT ^P law.     

Electrical conductivity and optical absorption studies on NiPc-substituted borate glass matrix

Electrical conductivity and optical absorption of nickel phthalocyanine (NiPc)-substituted borate glass is reported here for the first time. We have successfully prepared NiPc-substituted lithium borate glass at 850 °C and some preliminary studies on this glass are reported. Activation energy and optical band gap were determined for the glass from the Arrhenius plot of conductivity and optical absorption spectra, respectively.     

Electrical conductivity,relaxation, and scaling analysis studies of lithium alumino phosphate glasses and glass ceramics

Different compositions of lithium aluminum phosphate glasses were prepared by melt quenching technique. The best bulk conductivity achieved by the sample G₃, (28 mol% of lithium oxide). Further, the investigation extended by crystallizing the G₃ sample at different temperatures, 200 °C (GC₂₀₀), 300 °C(GC₃₀₀), 400 °C (GC₄₀₀), and 500 °C (GC₅₀₀). The electrical measurements for all the glasses and glass ceramics were carried out in the frequency range of 1–10⁵ Hz and at a temperature range of 393–513 K by the impedance spectroscopy. The variation of conductivity with frequency of the samples was explained in the light of different valency states of aluminum ions. AC conductivity data are fitted to a power law equation. Scaled spectra for ac conductivity and modulus data suggested that the present glass samples follow temperature independent conductivity distribution relaxation mechanism.     

Electrical conductivity of field-assisted ion-exchanged glass with molten PbCl2 salt

Field-assisted ion-exchange was carried out between soda-lime-silica glass tubes and molten PbCl₂ at 823 K for 2 h under constant potential of 12 V. The field-assisted ion-exchange leads to the formation of a lead-exchanged layer underneath the glass surface. The influence of the exchange on the bulk d.c. and a.c. electrical conductivity was investigated and compared with that of the glass before ion-exchange. The d.c. conductivity of the exchanged glass showed an activation energy higher than that of the glass before ion-exchange. The higher activation energy was attributed to the lower mobility of lead cations in the exchanged layer in comparison with that of sodium cations. The a.c conductivity of the exchanged glass showed an increase in the dielectric constant and a decrease in the dielectric loss. These findings suggest that lead cations enter the glass network in modifying positions in the exchanged glass. The results also support the data previously obtained that one lead cation from the molten PbCl₂ replaced two sodium cations from the glass.     

高热导率无机填料／硅橡胶复合绝缘材料的电性能

分别添加不同含量的微米Al2O3（0．5～3μm）、微米Si3N4（O．3～3μm）和纳米Al2O3（13nm）,利用共混法制备了具有不同导热性能的无机填料／硅橡胶复合材料。填料体积分数为30％时,通过改变微米Si3N4和纳米Al2O3体积比,发现微米Si3N4和纳米Al2O3共填充的硅橡胶复合材料的热导率较微米Si3...     

Electrical conductivity based characterization of plain and coarse glass powder modified cement pastes

This paper describes the use of electrical conductivity to characterize plain and coarse glass powder modified cement pastes. It is observed that the glass powder addition facilitates improved hydration of the cement grains. For the proportions investigated in this study, and the particle size of glass powder, this advantage is negated by the reduced amount of hydration products, i.e., the dilution effect. The variation of electrical conductivity and its derivative with time can be related to the various phases in the microstructural development of the paste. It is observed from the time derivative of conductivity plots that the addition of glass powder results only in minor changes in the setting time of the pastes. Higher the glass powder content, higher the normalized conductivity (ratio of conductivity at a certain glass powder content to that of plain paste) at very early times, and then it falls to a value closer to or less than 1.0 at later times. A parallel model is used to represent effective conductivity as a function of the pore solution conductivity, porosity, and pore connectivity factor. The pore solution conductivity increases with increase in glass powder content. The porosity of the pastes reduces with increase in glass powder content at early ages and increases at later ages. A reduced pore connectivity factor is observed for pastes with higher glass powder content at later times. However, this does not imply increased volume of hydration products as is commonly interpreted for normal pastes, but the electrical conduction pathways are made more tortuous by the relatively large volume of un-reacted filler material in the pore structure.     

Preparation and properties of hollow glass bead filled silicone rubber foams with low thermal conductivity

Silicone rubber foams filled with various content and different particle size of hollow glass bead (HGB) were prepared by compression molding. It was revealed that compared with silica filled silicone rubber foams, HGB filled materials achieved higher foaming extent, lower thermal conductivity, and lower hardness, which can be significant for thermal insulation materials. For HGB filled materials, the morphology indicated the average cell size decreased with higher HGB content and larger particle size of HGB. The density, thermal conductivity, hardness and tensile strength increased with higher HGB content and larger particle size of HGB.     

Electrical conductivity and ESR of lithium borate glasses containing mixed transition metal oxides

Electron spin resonance, optical spectra and d.c. electrical conductivity of 2Li₂O · 3B₂O₃ glasses doped with V₂O₅ and CuO were investigated. Spin Hamiltonian parameters of transition metal (TM) ions have been determined. The theoretical optical basicity _th of these glasses has been calculated and related to the spin-Hamiltonian parameters of TM ions. The variation of electrical conductivity with composition has been explained.     

Frustration, connectivity, and the glass transition

The concepts of connectivity, localization, and frustration are explored in relation to glass formation in amorphous materials. First, the concept of eigenclusters to geometrically characterize correlations in amorphous materials is introduced, and discussed in detail for both the Ising ferromagnet and Ising spin glass models. Second, a new, glass-forming percolation model that contains frustration as the essential ingredient, and exhibits two percolation transitions, is discussed. This new model gives new insights into frustrated systems, and applications to the Ising spin glass model and other glass-forming systems are discussed. In particular, we propose the possibility that the occurrence of a percolation-type transition at temperatures above the glass transition temperature may be a general feature of glass-forming systems. The important role of computer simulations in probing the mechanism of glass formation is emphasized.     

Electrical conductivity and thermoelectric power of amorphous Sb2Te3 thin films and amorphous-crystalline transition

The results of electrical conductivity and thermoelectric studies on antimony telluride, a promising thermoelectric material, in the thin film state are reported. Films were vacuum-deposited on to clean glass substrates with thickness between 50 and 200 nm and studied in the temperature interval 300 to 470 K. On heating the as-grown films, there is a sharp fall both in the Seebeck coefficient and the electrical resistivity at around 340 to 370 K for all the films. This is attributed to an amorphous to crystalline transition, which is confirmed by X-ray diffractogram and electron diffraction patterns.[/p]     

Electrical conductivity of Na3Zr2Si2PO12-doped sodium aluminosilicate glass

To improve the electrical conductivity of sodium aluminosilicate glass and Na₃Zr₂Si₂PO₁₂ crystal, crystal-glass composite systems were examined. For the ceramics with a lower content of the glass, the activation energy of ionic conduction was lowered and the conductivity enhanced by adding glass and the pre-exponential factor was lowered. Whilst the activation energy of ionic conduction of Na₂O-Al₂O₃-XSiO₂ (X=4, 6) glasses could not be lowered to the limiting value of ca. 0.5 eV, the glass-based sample doped with Na₃Zr₂Si₂PO₁₂ powder indicated that the high ionic conductivity and its activation energy was lowered to ca. 0.3 eV. The composite of Na₃Zr₂Si₂PO₁₂ crystalline powder and sodium aluminosilicate glass is a useful material to the solid electrolyte.     

Electrical conductivity in iron-containing oxide glasses

The electrical properties of silicate, borate, phosphate and tellurite glasses containing iron are reviewed. The highest electrical conductivity has been observed in iron-tellurite glasses. The problem of the structure and influence of different glass modifiers on the electrical conduction of iron-containing glasses is discussed.     

Electrical conductivity in hot-pressed nitrogen ceramics

The a.c. and d.c. electrical conductivities of some hot-pressed polycrystalline nitrogen ceramics have been measured between 400 and 1000° C. The materials examined were Si₃N₄, 5.0% MgO/Si₃N₄ and two sialons, Si_(6–z) · Al _z · O _z · N_(8–z) having z 3.2 and z 4.0 respectively. The electrical behaviour of all the materials showed similar general features. The d.c. conductivities were about 10^{–10 –1} cm^–1 at 400° C and rose to between 10^–6 and 10^{–5 –1} cm^–1 at 1000° C. The a.c. Data, taken over the frequency range 15 Hz to 5 kHz showed that below about 500° C the a.c. conductivity ( _a.c.) varied with frequency as _a.c. ^s where 0.7 _d.c.) agreed well with the relation _d.c. = A exp(–B/T ^1/4). Above 700° C both the a.c. and d.c. conductivities followed log T ^–1. Hall effect and thermoelectric power measurements enabled the Hall mobility to be estimated as less than 10^–4 cm² V^–1 sec^–1 at 400° C and showed that the materials were all p-type below 900° C and n-type above 900° C. The electrical properties of all four materials are consistent with the presence of a glassy phase.     

Electrical conductivity of yttrium-doped SrTiO3: influence of transition metal additives

The electrical conductivity of yttrium-doped SrTiO₃ with transition metals added as acceptor dopants (V, Mn, Fe, Co, Ni, Cu, Zn, Mo, Mg, Zr, Al, or Ga) was measured by the dc four-probe method at 600-900°C in reducing atmospheres. The replacement of 5 mol% titanium by acceptors leads to a decrease of conductivity of Sr_1−1.5xY_xTiO_3−δ. The degree of the decrease depends strongly on the type of dopant. Of the 5 mol% acceptor-doped compositions, the system Sr_0.85Y_0.10Ti_0.95Co_0.05O_3−δ had the highest conductivity of 45 S/cm at 800°C and oxygen partial pressure of 10⁻¹⁹ atm. The oxidation kinetics of yttrium-doped SrTiO₃ was significantly retarded by the addition of cobalt or manganese dopants. The ionic conductivity of SrTiO₃ doped with 5 mol% acceptors at Ti-sites was estimated from the total conductivity to lie in the vicinity of 10⁻⁴ S/cm, depending on oxygen partial pressure and temperature.     

Electrical conductivity of doped ZnS

The electrical conductivity of doped ZnS with different impurities (Mn, Fe, Co, Ni and Cu) of various concentrations has been measured to verify the existence of ladder-like levels of ‘killers’ of luminescence. Attempts have been made to ascertain the separation between the valence band of the host ZnS and the ground state of the acceptor impurities and also to investigate the effect of various concentrations of impurities on the electrical conductivity of doped ZnS.     

Electrical conductivity of polycrystalline semiconductors

A phenomenological model for the electrical conductivity in polycrystalline semiconductors is presented, using the assumption that an isotype heterojunction with a certain interface state density exists at the grain-intergrain domain interface. Tunnelling, thermionic emission of carriers through the intergrain barriers and ohmic conductivity of the heterojunction are all considered as possible charge transfer mechanisms. Explicit calculations are performed for wide-gap n-type semiconductors and a general expression is derived for the electrical conductivity. It is shown that the known models of Petritz and van den Broek, and also the expression for the conductivity of monocrystalline semiconductors, are special limiting cases of the theory presented.     

The superionic Agl-Ag2O-V2O5 system: Electrical conductivity studies on glass and polycrystalline forms

Superionic conducting glasses in the Agl-Ag₂O-V₂O₅ system were prepared by heating the appropriate amounts of raw materials at 723 K and quenching in liquid nitrogen. The polycrystalline materials were prepared by slowly cooling the melt to room temperature. X-ray diffraction was used for material characterization. The electrical conductivity of the pulverized samples, pressed together with an electrode mixture of silver and electrolyte (1:2 by weight) under 5000 kg cm^–2 pressure to form pellets 10 mm in diameter and 2 to 3 mm in thickness, was measured in the temperature range 300 to 365 K at 1 kHz. The ionic conductivities of the glasses were always higher than those of their polycrystalline counterparts, while their activation energies were also slightly higher. Conductivity measurements on annealed glassy samples indicated that the conductivity decreases with the time of annealing, and reaches a constant value which is nearly the same as that of the polycrystalline sample. Electronic conductivities of both types of sample were obtained by using Wagner's polarization cell technique, which showed that the electronic conductivity for both types was five orders of magnitude less than the total conductivity. Typical galvanic cells having the configuration Ag,electrolyte/electrolyte/C,electrolyte,I₂ were constructed and the silver ion transport number was calculated by the e.m.f. method.     

Electrical conductivity, thermoelectric power and viscosity of liquid Sn-based alloys

Shear viscosity of liquid Sn–Ag, Sn–Cu and Sn–Ag–Cu eutectics from melting temperature up to 1100 K and their electrical conductivity and thermoelectric power up to 850 K have been investigated. The electrical properties of liquid Sn with additions of Fe and Ni have also been studied. It is shown that small amounts of metal admixtures affect noticeably the behavior of the physical properties of liquid Sn.     

Electrical conductivity,structure and hall effect measurements of InSe films

Stoichiometric InSe films were prepared by discrete evaporation using spectrally pure (99.999%) InSe powder in a residual pressure of about 4×10^?6 Torr. The thickness of the films was varied from 500 to 3000 Å. The elctrical conductivity of the films was measured by Van der Pauw's method. The as-deposited films had an amorphous structure as observed with an electron microscope. Thermal annealing was carried out through a number of annealing cycles and a transformation to a crystalline state during the process was evidenced by the electron micrographs. Conductivity measurements were made on the amorphous films from the transition temperature to liquid air temperature and the activation energies were calculated from the variation in conductivity with temperature. The density of states at the Fermi level was also calculated at low temperatures. Hall effect measurements were made on the annealed films and the Hall mobility μ_H, the Hall coefficient R_H and the carrier concentration n were evaluated.