NONLINEAR PHENOMENA IN COMPLEX SYSTEMS
An Interdisciplinary Journal

2003, Vol.6, No.2, pp.619-629


Are Hoping Theories of Electrical Conductivity Applicable to Explain Ionic Conduction? The Chalcogenide Composition as an Example
S. A. El-Hakim

This work deals with the determination of the ratio between the correlation length and the radius of localization (a), , from the analysis of the ac conductivity in the temperature range 300-77 K, and in the frequency range 50Hz - 80kHz, in composition prepared by ice-water quenching technique. The composition has a mixed ionic and electronic conductivity. The reduced activation energy method and percolation theories of conductivity are applied to the ac conductivity of the prepared composition. From the analysis of the scaled curve of conductivity, the random walk dimension is obtained. In the temperature range 133 K < T < 173 K, the conductivity mechanism is site or bond percolation. But in the temperature range room temperature > T > 173, K, the conductivity is due to normal diffusion character. The onset of the frequency dependent conductivity is 12.5 kHz, and the crossover frequency from fractal regime of conductivity to hoping regime is 40 kHz. The radius of localization is determined and found to increase with increasing frequency, also the same behavior is observed in correlation length. The ratio is determined and characterized by its slightly dependence on frequency in the range f < 17.5 kHz. But in the frequency range f > 17.5 kHz the ratio is independent on frequency. This behavior is the same at all temperatures in the range of the present investigation. The activation energy of relaxation is found to equal to 0.048 eV.
Key words: correlation length, hoping conduction, fractal

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