Search results for "Surface conductivity"

showing 3 items of 13 documents

Microwave response of a cylindrical cavity made of bulk MgB2 superconductor

2008

We report on the microwave properties of a resonant cylindrical cavity made of bulk MgB2 superconductor, produced by the reactive liquid Mg infiltration process. The frequency response of the cavity has been measured in the range 5-13GHz. Among the various modes, the TE011, resonating at 9.79GHz, exhibits the highest quality factor. For this mode, we have determined the temperature dependence of the quality factor, obtaining values of the order of 10^5 in the temperature range 4.2-30K. The values of the surface resistance deduced from the measurements of the quality factor agree quite well with those independently measured in a small sample of MgB2 extracted from the same specimen from whic…

SuperconductivityFrequency responseMaterials scienceCondensed matter physicsMgB2Condensed Matter - SuperconductivitySettore FIS/01 - Fisica SperimentaleFOS: Physical sciencesEnergy Engineering and Power TechnologyAtmospheric temperature rangeCondensed Matter PhysicsElectronic Optical and Magnetic MaterialsSuperconducting microwave cavitySuperconductivity (cond-mat.supr-con)Surface conductivityQuality (physics)Surface resistanceElectrical and Electronic EngineeringSheet resistanceMicrowaveMicrowave cavity
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Fluxon dynamics by microwave surface resistance measurements in MgB2

2003

Field-induced variations of the microwave surface resistance, Rs(H), have been investigated in high-density ceramic MgB2. At low temperatures, several peculiarities of the Rs(H) curves cannot be justified in the framework of models reported in the literature. We suggest that they are ascribable to the unconventional vortex structure in MgB2, related to the presence of two gaps. On the contrary, the results near Tc can be accounted for by the Coffey and Clem model, with fluxons moving in the flux-flow regime, provided that the anisotropy of the upper critical field is taken into due account.

SuperconductivityPhysicsFluxonCondensed matter physicsCondensed Matter - SuperconductivityFOS: Physical sciencesEnergy Engineering and Power TechnologyTourbillonMgB2 Microwave surface impedance Fluxon dynamicsCondensed Matter PhysicsMagnetic fluxElectronic Optical and Magnetic MaterialsVortexSuperconductivity (cond-mat.supr-con)Surface conductivityCondensed Matter::SuperconductivityElectrical and Electronic EngineeringAnisotropyCritical fieldPhysica C: Superconductivity
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Modeling of surface vs. bulk ionic conductivity in fixed charge membranes

2003

A two-region model for describing the conductivity of porous fixed charge membranes is proposed. In the surface region, the conductivity is due to the mobile positive ions (counterions) around the negative fixed charges. In the pore center region, the conductive properties resemble those of the external electrolyte solution because the fixed charges are assumed to be effectively neutralized by the counterions in the surface region. Activation energies and surface diffusion coefficients are estimated by assuming that the counterion jump from a fixed charge group is the rate limiting process for surface transport. The barrier energy for this jump is calculated using a simple electrostatic mod…

inorganic chemicalsSurface diffusionchemistry.chemical_classificationPhysics::Biological PhysicsChemistryAnalytical chemistryGeneral Physics and AstronomyThermodynamicsElectrolyteConductivityIonSurface conductivityMembraneIonic conductivityPhysical and Theoretical ChemistryCounterionPhys. Chem. Chem. Phys.
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