Features of the spectral characteristics of conductivity fluctuations of dispersed systems near the percolation threshold
D.V. Tsypin1, S.S Volchkov1, D.A. Zimnyakov1, 2;
1Yury Gagarin State Technical University of Saratov, 77 Polytechnicheskaya st., Saratov, 410054, Russia;
2Institute for Problems of Precision Mechanics and Control RAS, 24 Rabochaya st., Saratov, 410028, Russia.
Abstract
The results of experimental studies of features of the spectral characteristics of conductivity fluctuations of dispersed systems near the percolation threshold are presented. At the final phase of degradation, analyzing the voltage decreases across the samples reveals a critical exponent of approximately 1.597 for the ohmic conductivity. At the early stage of degradation, the spectral density of conduction current fluctuations within the frequency range of 0.01 Hz to 1 Hz decreases approximately as 1/ω, while near the percolation threshold, the decreasing trend changes to 1/ω². This transition is explained by the growing impact of blockages and subsequent avalanche-like breakdowns of some local conduction pathways within the bridges, leading to electron transport near the percolation threshold. Spectral density of conduction current fluctuations can be recovered from the spectral density of voltage drop fluctuations applying the renormalization factor. The power spectra of fluctuations in voltage drops commonly show a decay that closely follows a power law pattern. A decrease in the spectral exponent γ of conduction current fluctuations down to the values close to -2 indicates emergence of a new mechanism that controls a transfer of mobile charge carriers at the stage of significant conductivity decay. It is important to highlight the significantly elevated noise levels observed in these systems, as indicated by the normalized root-mean-square values of conduction current fluctuations during the quasi-stationary phase.
Speaker
D.V. Tsypin
Yury Gagarin State Technical University of Saratov
Russia
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