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Article Citation - WoS: 3Citation - Scopus: 3Effect of Ionic Substitution on the Structural, Dielectric and Electrical Properties of Bismuth Zinc Niobate Ceramics(Korean Assoc Crystal Growth, inc, 2012) Qasrawi, A. F.; Abu Je'ib, Hussein A.; Mergen, A.; Department of Electrical & Electronics EngineeringThe effects of tin substitution on the structural, dielectric and electrical properties of the Bi1.5Zn0.92Nb1.5O6.92 pyrochlore ceramics have been investigated. Tin atoms was substituted in the A (Bi1.5Zn0.46)-site instead of zinc and in the B ((Zn0.46Nb1.5)-site instead of niobium in accordance to the chemical formulae Bi1.5Zn0.92Nb1.5-xO6.92-x/2 and (Bi1.5-x/3Zn0.46-3x/2Snx)(Nb1.5Zn0.46)O-6.92, for 0.00 <= x <= 0.40 and 0.00 <= x <= 0.60, respectively. A relative single phase formation of the structures was possible for x values less than 0.25 and less than 0.10. Pronounced tunability in the dielectric constant values associated with very low dielectric loss are obtainable by Sn substitution. Furthermore, a frequency invariant but linearly varying temperature dependent dielectric constant is observed. The electrical conductivity decreased by two and one order of magnitude for the A and B-site substitutions, respectively. The temperature-dependent conductivity analysis in the temperature region of 300-500 K, reflected the existence of shallow and deep impurity energy levels being created by the doping process.Article Citation - WoS: 1Citation - Scopus: 1Cobalt Doping Effects on the Mechanical and Electrical Parameters of Bi1.5zn0.92< Solid Solution(indian Ceramic Soc, 2014) Qasrawi, A. F.; Jaradat, Haneen N. M.; Mergen, A.The cobalt doping effects on the lattice constant, strain, grain size, dislocation density and electrical conduction are investigated by means of X-ray diffraction and electrical resistivity measurements on the Bi1.5Zn0.92Nb1.5-xCoxO6.92-x (x=0.03-0.20) ceramics, respectively. Increasing cobalt content sharply increases compressing strain and dislocation density and decreases both the lattice constant and the grain size of the pyrochlore. At a doping content of 0.05 new minor phase of ZnO appears. The ZnO grains increase with increasing cobalt content. When the cobalt doping is repeated in accordance with the formula Bi1.5Zn0.92Nb1.5-xCoxO6.92-x, a single phase pyrochlore is obtained with cobalt content up to 0.10. The electrical resistivity analysis reflects increasing activation energy with increasing cobalt content. The cobalt creates an impurity level in the energy gap of the pyrochlore that shifts towards the mid gap converting the extrinsic nature of conductivity to intrinsic at a cobalt content of 0.10.Article Citation - WoS: 1Citation - Scopus: 1Structural, Optical and Electrical Properties of Ybinse Thin Films(Elsevier Science Sa, 2016) Alharbi, S. R.; Qasrawi, A. F.In this work, the compositional, the structural, the vibrational, the optical and the electrical characterizations of the YbInSe compound are investigated by means of energy dispersion X-ray analysis, scanning electron microscopy and X-ray diffraction, Raman spectroscopy, ultraviolet-visible light spectrophotometry, impedance spectroscopy and temperature dependent electrical conductivity, respectively. The 300 nm thick YbInSe films which were prepared by the co-evaporation of the source materials under a vacuum pressure of 10(-5) mbar, are observed to exhibit nanocrystalline clusters of size of 27 nm regularly distributed among an amorphous structure. The most intensive Raman active lines are observed at 150 and 254 cm(-1). In addition, the optical analysis has shown that the films exhibit a direct forbidden electronic transitions type energy band gap of 1.07 eV. The optical transitions are associated with interband tail states of width of 0.28 eV. Moreover, the real and imaginary parts of dielectric spectra which were analyzed in the frequency range of 270-1000 THz, were analyzed in accordance with the single oscillator and the Lorentz models, respectively. The modeling allowed determining the oscillator and dispersion energies, the terahertz free carrier scattering time, the free holes effective mass, the carrier density, the drift mobility and the reduced resonant frequency for the YbinSe films. In the electronic part of study, the temperature dependent dc electrical conductivity analysis, indicated the domination of the variable range hopping transport mechanism below 335 K, the thermal excitation of charge carriers in the range of 337390 K and the extrinsic-intrinsic transition property at 390 K. The ac conductivity spectra which were recorded in the frequency range of 10-1500 MHz, revealed the domination of the correlated barrier hopping of free carriers between pairs of localized states at the Fermi level. (C) 2016 Elsevier B.V. All rights reserved.
