Relaxation in systems with exponential or Gaussian distributions of activation energies
New expressions are presented, simplified, and discussed for the small-signal-frequency response of systems involving distributions of activation energies with either exponential or Gaussian probability densities. The results involve the possibility of separate but related thermal activation of energy storage and energy loss processes, and apply to the response of both dielectric and conductive systems. Response with a Gaussian distribution of activation energies (GDAE) may be either symmetric or asymmetric in log frequency, and typical GDAE responses are compared with those associated with several exponential distributions of activation energy (EDAE) models, using complex nonlinear least squares fitting. The GDAE model does not lead to the frequently observed fractional exponent power-law response in time or frequency as does the EDAE; thus, the GDAE cannot fit any EDAE response well which involves an appreciable range of such behavior, but is found that, conversely, the general EDAE model can often fit a GDAE response very well over a wide frequency range. Recent (KBr)0.5(KCN)0.5 dielectric data covering a range from T=13.7 to 34.7K are analyzed and the GDAE is found to yield the best overall fits. The present analysis suggests an alternative to the earlier results and suggestions that the width of the probability-density distribution increases with decreasing temperature and that the activation energies or barrier heights themselves depend linearly on temperature.
- Research Organization:
- North Carolina Univ., Chapel Hill (USA). Dept. of Physics and Astronomy
- OSTI ID:
- 6312679
- Report Number(s):
- AD-A-180876/5/XAB
- Resource Relation:
- Other Information: Pub. in Jnl. of Applied Physics, Vol. 61, No. 2, 700-713(15 Jan 1987)
- Country of Publication:
- United States
- Language:
- English
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