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