[en] The I-V characteristic curves were studied in the temperature range 301-359 K and pressure range up to 7.15 x 10⁹ Pa which illustrate a non-linear behaviour below (high-resistance region) and beyond (negative-resistance region) a breakdown point characterising Ge₂₇Te₆₂Se₁₁ chalcogenide glasses. The general behaviour is shifted towards lower voltage and higher current when the ambient temperature and/or the applied pressure were increased. The non-linear behaviour in the pre breakdown region is discussed according to the Poole-Frenkel field emission of electrons from deep traps located at a depth equal to 0.372eV. The analysis of the effect of field on the non-linear conduction in Ge₂₇Te₆₂Se₁₁ chalcogenide glass suggests a modification of the energy difference between filled and empty sites, where the effect of pressure suggests a reduction of the energy gap width. The analysis based on simple thermal effects in the region closer to the breakdown point implies the electrothermal process initiating the negative resistance region. The results of post breakdown region (negative-resistance region) imply the electron hopping between filled and empty localised states at Fermi level. The density of localised states is estimated which lies in the range 5.7 x 10¹⁶-1.84 x 10¹⁸cm^-3/eV

[en] Samples of η-alumina ceramic in powder form were prepared according to the standard methods. The electrical conduction of γ-irradiated and unirradiated alumina was studied between room temperature and 673 K. An anomalous behaviour in σ-1/T relations is observed for all investigated samples. This behaviour is based on an attenuation in conductivity values in the relatively low temperature range followed by an activation in their values passing through minimum at characteristic temperature T*. The attenuation of conductivity with increasing temperature is explained according to the thermal quenching of mobile charge carrier as well as proton-phonon scattering. The activation of conductivity with increasing temperature beyond T* is explained on the basis of thermal activation of charge carriers from deep traps spread at energy levels between 0.44 and 0.5 eV. In addition, a remarkable increase in conductivity values is recorded with increasing γ-radiation dose which is discussed according to the primary ionization effects of radiation. (author)

[en] The effect of both composition and creation of the crystalline phase in (V₂O₅)_1-x(P₂O₅), glasses, where x=0.10, 0.15, 0.20 and 0.25, on both I-V characteristic curves and ac conductivity are studied in the temperature range 303-473 K. The I-V characteristics show non-linear behaviour below and beyond a turnover point (switching point) characterizing these glasses. This turnover point is shifted towards lower voltage and higher current as the vanadium, the ambient temperature or the degree of crystallinity in the glass were increased. The results are interpreted according to the Poole-Frenkel emission of electrons under high field between filled V⁴⁺ and empty V⁵⁺ sites in the region below the turnover point. The conduction in the negative-resistance region (beyond the turnover point) is discussed according to the hopping of electrons between filled and empty sites under high field, joule heating and self-generation of ac signal. The frequency dependence of the ac conductivity satisfies the power law relation, σ(ω)≅ω⁸, which explains the quantum-mechanical hopping of single electrons in the disordered matrix

[en] Gamma irradiation effects on the electrical conductivity behaviour of the double complexes [Co(NH₃)₆] [Co(CN)₆], [Co(NH₃)₆] [Al(CN)₆] and [Co(NH₃)₆] [Mn(CN)₆] were investigated. A comparison is made between the rates and activation energies of thermal annealing of electrical properties of pure and γ-irradiated samples. The conductivity of the solid double complexes increases with temperature, decreases with radiation dose, and remarkably increases when the transition metal of the negative component of the double complex changes from Al to Mn to Co. However, the results show that the rate constants and activation energies of thermal annealing of defects in these systems are not significantly affected by gamma irradiations. (author)

[en] PVA: Co₅(OH)₈(NO₃)₂•2H₂O polymer composite has been produced by casting of aqueous solution of mixed composite component. The nano polymer composites were characterized using structure techniques; XRD, SEM, FT-IR and TGA. The results indicated the formation composite without PVA degree of crystallinity variation. The measurements of electrical conductivity for the composites illustrated domination of ion conduction with activation energy (0.65-0.90) eV. The optical absorption illustrated an absorption peak around (530-540) nm which suggest electronic direct transition via energy gap width (1.90-2.16) eV. The electrochemical illustrated electrochemical band gap (1.97-3.26) eV

[en] Mono-, homo-bi- and hetero-binuclear metal chelates of N,N'-ethylene bis-salicylideneimine were prepared according to the standard methods. The effect of thermal treatment on the electrical conductivity of gamma irradiated and unirradiated metal chelate complexes was studied from room temperature up to 463K. All investigated samples showed an activation in the electrical conductivity with increasing temperature and reduction in its value with gamma irradiation. The rate constants of isothermal annealing reaction and the activation energy of the electrical conduction in the irradiated and unirradiated complexes are calculated and discussed. (author). 3 tabs., 3 figs., 10 refs