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Article Citation - WoS: 7Citation - Scopus: 9Properties of Boron Doped Ti-Ba Superconductors(Pergamon-elsevier Science Ltd, 2003) Kayed, TSThe effects of boron doping on the formation and properties of the Tl-based superconductors have been studied. Up to 10 wt.% boron has been added to the oxides having the nominal composition, Tl1.8Ba2Ca2.2Cu3Ox, by the usual solid-state reaction method. Boron additions in the range 0.8-1.0% increase the fraction of the Tl-2223 phase and significantly improve the critical temperature of the samples. Higher amounts of boron additions eliminate the Tl-2223 phase, reduce the fraction of Tl-2212 phase and cause separate non-superconducting phases to be formed. The formation of non-superconducting phases does not allow us to obtain pure Tl-2212 phase. (C) 2002 Elsevier Science Ltd. All rights reserved.Article Citation - WoS: 5Citation - Scopus: 5Electrical Behavior of Pb1.83mg0.29< Pyrochlore Ceramics(Elsevier Science Bv, 2004) Mergen, A; Kayed, TSPb1.83Mg0.29Nb1.71O6.39 pyrochlore was produced via a simple partial oxalate method. It was examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Single phase, belonging to the cubic pyrochlore structure, with a lattice parameter of a = 10.60125 +/- 0.001 Angstrom and grain size that varies from 5 to 10 mum was obtained. The electrical properties were measured at different temperatures in the range 15-320 K without and with applied magnetic field of 1.4 T. Current-voltage characteristics data were fitted to a power law expression V=I-beta(T) in which the exponential parameter beta takes values around 1 at all temperatures except at 300 K. Resistance starts from 3.3 x 10(10) Omega at 15 K and increases gradually to 4.8 x 10(10) Omega at 240 K. It drops to approximately 1.2 x 10(10) Omega at 300 K, after which it increases again to around 1.6 x 10(10) Omega at 320 K. (C) 2004 Elsevier B.V. All rights reserved.Article Citation - WoS: 1Citation - Scopus: 1Optoelectronic Properties of Tl3inse4 Single Crystals(Taylor & Francis Ltd, 2010) Qasrawi, A. F.; Gasanly, N. M.The crystal structure, temperature-dependent electrical conductivity, Hall coefficient, current-voltage characteristics, absorption spectra and temperature- and illumination-dependent photoconductivity of Tl3InSe4 single crystals were investigated. Tl3InSe4 crystallises in a body-centred lattice with tetragonal symmetry and belongs to the space group [image omitted]. The crystals are extrinsic p-type semiconductors and exhibit a conductivity conversion from p- to n-type at a critical temperature, Tc, of 283 K. They are observed to have Schottky diode properties in an Ag/Tl3InSe4/Ag Schottky barrier device structure. The absorption spectra displays two maxima, one related to an indirect energy band gap of 1.20 eV and another corresponding to exciton transitions. The photocurrent is observed to be strongly affected by the conductivity type of the crystal. The incident light intensity dependence of the photocurrent is found to be supralinear, linear and sublinear, indicating strong recombination at the surface, monomolecular recombination and bimolecular recombination, respectively, in the regions where the sample is p-type ([image omitted]), at [image omitted], and in the n-type region ([image omitted]). In the n-type region, the photocurrent increases with decreasing temperature down to 250 K, below which the photocurrent is temperature invariant. The change in recombination mechanism is attributed to the change in the behaviour of sensitising and recombination centres.
