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Effect of sulfur doping on the dielectric properties of Sb_(2)Se_(3) system

Journal of Advanced Dielectrics 2019年第1期9卷 1-5页

作者： ragab mahani E.A.El-Sayady Microwave Physics and Dielectrics Department National Research Centre 33 EL Bohouth St.(Former EL Tahrir St.)GizaP.O.12622Egypt Solid State Physics Department National Research Centre 33 EL Bohouth St.(Former EL Tahrir St.)GizaP.O.12622Egypt

In this paper,we report the effect of sulfur doping on the electrical and dielectric properties of semiconducting Sb_(2)Se_(2)S over wide ranges of temperatures(298–473 K)and frequencies(42–10^(6) Hz).Sb_(2)Se_(2)S system has been prepared by the direct fusion and cooling cycle of a mixture of the constituent elements,in stoichiometric ratio and purity 99.999%,in vacuum-sealed silica tubes.X-ray analysis showed a decrease in the cell parameters a,b and c upon doping with ***,the pure and doped Sb_(2)Se_(3) showed the single orthorhombic phase *** permittivity of Sb_(2)Se_(2)S showed a decrease with increasing frequency due to a decrease in the average bond ***,ac conductivity increased with the frequency increase,obeying the Jonscher’s universal dynamic *** conductivity temperature dependence is well described by the correlated barrier hopping *** activation energy calculated from DC conductivity is found at higher value(0.79 eV)as compared to that reported in the literature for other antimony selenide ***,a new Sb_(2)Se_(2)S compound is suggested which may be useful for electronic devices.

关键词： Antimony selenide permittivity frequency

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Doping effect of SrZrO_(3) on KNLN ceramics structure and their dielectric properties

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Journal of Advanced Dielectrics 2018年第5期8卷 28-34页

作者： Emad Ewais ragab mahani Samy Mostafa Adel Ahmedx Refractory and Ceramic Materials Division(RCMD)Central Metallurgical R&D Institute P.O.87 Helwan 11421 CairoEgypt Microwave Physics and Dielectrics Department National Research Centre 33 EL Bohouth st.(former EL Tahrirst.)P.O.12622 GizaEgypt Tabbin Institute for Metallurgical Studies(TIMS)P.O.109 Helwan 11421 CairoEgypt Chemistry Department Helwan University HelwanCairoEgypt

In this work,lead-free systems;(1-x)(K_(0.465)Na_(0.465)Li_(0.07))NbO_(3)–xSrZrO_(3)(x=0,0.005,0.050,0.095 and 0.14)were synthesized by the conventional solid-state reaction ***,SEM,densification parameter as well as dielectric parameters of the obtained KNLN ceramics were *** analysis showed the formation of orthorhombic perovskite structure in all investigated ***_(3)(SZ)inhibited the grain growth and increased the distribution of grains uniformly in the micro*** addition,SZ changed the crystalline system of KNLN ceramics *** a consequence,the permittivity,dielectric loss as well as AC conductivity decreased *** ceramics of x=0.005 are characterized by low conductivity(10-10 S/cm),low dielectric loss(0.005)and relatively high permittivity(34).They can be useful for the electrical capacitors fabrication and filtering out noise from signals in resonant *** frequencies lower than 105 Hz,DC conductivity and separation of the charges at the interfaces were found to dominate the electrical behavior of ceramics,whereas at higher frequencies,a faster or dipole polarization may become more dominated.A broad peak has been observed in the imaginary part of electric modulus revealing to the non-Debye dielectric relaxation *** mechanical tunneling(QMT)was found to be the most suitable to characterize the electrical conduction mechanism in the ceramic compounds.

关键词： Lead-free ceramics KNLN dielectric properties.

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Structural and AC electrical properties study of solid metal urea complexes

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Journal of Advanced Dielectrics 2018年第2期8卷 60-66页

作者： ragab mahani Saleh D.Mekky Badr A.El Sayed Gamal S.EL-Bahy Azza Ward Microwave Physics and Dielectrics Department National Research Centre 33 EL Bohouth St.(former EL Tahrir St.)Giza-Egypt-P.O.12622 Chemistry Department Faculty of ScienceAlazhar University Nasr CityCairoEgypt Spectroscopy Department National Research Centre 33 EL Bohouth St.(former EL Tahrir St.)Giza-Egypt-P.O.12622

The complexation of solid urea with(Co^(2+)),(Cu^(2+))or(Ni^(2+))ions has been studied by using dielectric spectroscopy technique over a wide frequency range at different temper ***'structure were investigated by XRD,FTIR and FT-Raman *** and Raman analy sis indicated that the urea coordinates with the metal atoms through the same oxygen-metal bond(O-M).Furthermore,XRD analysis showed that the samples have polycrystalline structure with single *** pemittivity of complexes was found at much higher values than that of the ligand(pure urea),showing structure ***,two relaxation peaks were observed in the dielectric loss spectra corresponding to the orientation po larization of urea molecule,and some parts of urea molecule may be NH2 *** relaxation peaks correspond to thermally activated because they were shifted to higher frequency with the temperature *** peak position for the low frequency relaxation peak was observed lht the same relaxation time(τ=7.6× 10^(-4) s),corresponding to the coordination mode through the same O-M *** of this work is the successful finding of the relationship between the crystalline phase,coordination mode and the dy namic molecular behavior of solid urea and its complexes using the dielectric spec-troscopy techn ique.

关键词： Urea complexes IR XRD permitivity

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