Search results for "conductivity"
showing 10 items of 1988 documents
On the use of tin–lithium alloys as breeder material for blankets of fusion power plants
2000
Abstract Tin–lithium alloys have several attractive thermo-physical properties, in particular high thermal conductivity and heat capacity, that make them potentially interesting candidates for use in liquid metal blankets. This paper presents an evaluation of the advantages and drawbacks caused by the substitution of the currently employed alloy lead–lithium (Pb–17Li) by a suitable tin–lithium alloy: (i) for the European water-cooled Pb–17Li (WCLL) blanket concept with reduced activation ferritic–martensitic steel as the structural material; (ii) for the European self-cooled TAURO blanket with SiCf/SiC as the structural material. It was found that in none of these blankets Sn–Li alloys woul…
Ion irradiation of AZO thin films for flexible electronics
2017
Aluminum doped Zinc oxide (AZO) is a promising transparent conductor for solar cells, displays and touch-screen technologies. The resistivity of AZO is typically improved by thermal annealing at temperatures not suitable for plastic substrates. Here we present a non-thermal route to improve the electrical and structural properties of AZO by irradiating the TCO films with O+ or Ar+ ion beams (30–350 keV, 3 × 1015–3 × 1016 ions/cm2) after the deposition on glass and flexible polyethylene naphthalate (PEN). X-ray diffraction, optical absorption, electrical measurements, Rutherford Backscattering Spectrometry and Atomic Force Microscopy evidenced an increase of the crystalline grain size and a …
Ab initio simulations on charged interstitial oxygen migration in corundum
2018
We have performed this work within the framework of the EUROfusion Consortium receiving funding from the European grant agreement 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. Authors thank R. Vila, A.I. Popov, A. Luchshik and R.A. Evarestov for fruitful discussions. To carry out large-scale calculations, we have used the HPC supercomputer at Stuttgart University (Germany)
Synthesis and characterization of cobalt silicide films on silicon
2006
Cobalt silicide has emerged as a leading contact material in silicon technology due to its low resistivity, high stability and small lattice mismatch. In this study, 0.2-0.4 mu m thick Co films were deposited on Si(100) wafers by RF magnetron sputtering at room temperature, and annealed at temperatures from 600 to 900 degrees C in vacuum. As-deposited and annealed samples were characterized by Rutherford backscattering spectrometry (RBS), nuclear reaction analysis (NRA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Although the Si substrates were sputter cleaned before the deposition, all the samples showed a thin oxide layer at the Si/Co interfaces. Annealing up to 700 d…
Luminescence Properties of ZnO Nanocrystals and Ceramics
2008
The luminescence excitation spectra, luminescence spectra and the nanosecond-scale decay kinetics were studied. The ZnO and ZnO:Al nanopowders were prepared by vaporization-condensation in a solar furnace using different raw powders: commercial, hydrothermal and those obtained by plasma synthesis. Exciton-phonon as well as exciton-exciton interaction processes in nanopowders, a bulk crystal and ZnO ceramics were studied and compared. The fast decay and low afterglow intensity of ZnO nanopowders and ceramics support these materials for scintillators.
CEMS of insulators by use of gas-flow counters
1994
Gas-flow CEMS counters are usually designed in such a manner that the sample to be investigated is inserted into the counter and serves as the backing cathode. If the sample consists of an insulating material, serious problems are expected by charging-up effects similar to those appearing in Maze counters. These problems are discussed in detail. It could be shown by experiments with glass samples that their very low surface conductivity is sufficient to allow a defined operation of such gas-flow CEMS detectors. The electric field strength between the surface of the sample and the anode has to be equal or higher than that between the entrance window and the anode. This can be ensured by an a…
Comparative study of electrical behavior and phase transitions in pure and chromium doped α-LiIO3single crystals
1999
Abstract The polymorphic phase transitions of undoped and chromium doped α-LiIO3 crystals have been investigated by means of DTA experiments at slow heating rates and electrical measurements vs temperature and frequency. Upon heating the well known α ⇔ γ ⇒ β sequence appears to be influenced by the sample's morphology, acidity of the growing solution and doping. Dielectric response at room temperature is close to the type “superposition of d.c. ionic conductivity and dipolar response”. We describe the thermal behavior of conductivity along the c polar axis at three frequencies. Electrical measurements also highlight a higher value of ionic conductivity and a less destructive transition for …
Transient and stable color centers in neutron irradiated MgO
2008
Abstract The transient absorption and luminescence induced by the pulsed electron beam have been investigated in the MgO single crystal containing transition metal ion (Cr, Mn, Fe) impurities and preliminary irradiated by the fast neutrons. It is supposed that the different behavior of the absorption spectra of the MgO samples preliminary irradiated by the different fast neutron fluence is connected with the destruction of the hole centers and with the creation of interstitial protons and the formation of the microphase Mg(OH)2. We assume that the luminescence band at ∼3.2 eV is connected with F+ color centers.
Ion diffusion-controlled thermally stimulated processes in x-ray irradiated halide crystals
2003
The ionic and ion diffusion-controlled thermally stimulated relaxation (TSR) processes in CaF2, BaF2, LiBaF3 and KBr crystals were investigated above 290 K by means of the ionic conductivity, ionic thermally stimulated depolarisation current (TSDC) and thermal bleaching techniques. Under a DC field the halide crystals store large ionic space charge. We were able to detect in CaF2, BaF2, LiBaF3 and KBr in the extrinsic ionic conductivity region a series of the ionic defect (the interstitial anion and/or anion vacancies - in fluorides; the cation vacancies - in KBr) release stages: 3-6 wide and overlapping ionic TSDC peaks. The correlated data of the ionic TSDC and the F band thermal show tha…
Induced optical absorption and ITS relaxation in LiNbO3
1999
Abstract Electron pulse induced absorption spectra and their decay kinetics have been investigated in LiNbO3 crystals with various Li/Nb ratios rasnging from congruent to stoichiometric composition. It is shown that the absorption spectra, the optical density and the decay kinetics depend on the Li/Nb ratio. The rising front of the induced absorption is too fast to be resolved. The room temperature decay, characterized by the half-lifetime Δt, is faster in the stoichiometric crystal (∼ 750 ns) than in the congrruent crystal (∼ 3.5 μs).