Title: Behavior of power fractional kinetics in condensed matters

Abstract

Kinetics of processes in condensed matters may be expressed in the form of ac frequency spectra of real and imaginary components (in the frequency domain) or in the form temporal decay after abrupt termination of exciting steady state field (in the time domain). Universal relaxation law is characterized by fractional power dependence of real and imaginary component of ac response with the same exponent 0 < n < 1 and widely observed in different classes of materials like amorphous glasses, ceramics, poly-crystalline and single crystals. In this report dispersive media means a system consisting of dynamical pieces characteristic times of which are distributed over wide temporal range according to fractional power law. One of the interesting feature of power dispersive solids are unexpectedly high relative dielectric constant let them name as colossal dielectric constant materials. There are a few models explaining their huge values, but they aren’t directly related to power fractional dispersion. The aim of this report is to describe behavior of power fractional kinetics on temperature and stress on spectra with exponent n within the range of about 0.7-0.9, formulate the kinetics features and universality in temperature and stress dependencies. Character of temperature behavior of power dispersive systems has been considered depending on a range of exponent n. The model of temperature behavior of dispersive systems is based on thermally activated behavior of efficient dipoles with different relaxation times. According to the model universality of temperature behavior of medium dispersive system has been described. Strong stress dependence of medium dispersive systems has been revealed. The proposed model shows that increase of real and imaginary parts of complex relative dielectric constant is accompanied with decrease of exponent n with increasing uniaxial stress. Sensitivity of parameters B and n of dielectric spectra and parameters of effective dipoles on uniaxial stress has been estimated for high-resistivity GaSe layered crystals.