Zero-frequency conductivity, temperature dependence

Fig. 8. Temperature dependence of the zero-frequency conductivity of the paired holon superconductor. The curve is indistinguishable for the three coupling strengths X 0.1, X= 0.5 and X= 1.2.

The Brillouin linewidth Td) depends on the dynamic shear and volume viscosities r s(w) and t v(w). If the hypersonic shear viscosity r s(Aa)(i)) is equal to the zero frequency shear viscosity and the small term caused by thermal conductivity is neglected, then measurements of Td) can be used to obtain the volume viscosity. Champion and Jackson (8) noticed that the volume viscosities determined in the above manner for the n-alkanes were essentially independent of temperature. The values of r(i) measured in the authors laboratory for n-hexadecane are plotted... 

Conductive-system dispersion (CSD) usually involves thermally activated conduction extending to zero frequency plus an always-present bulk dielectric constant, usually taken to be frequency-independent in the experimental range. Dielectric-system dispersion (DSD) often involves dielectric-level response with only weak temperature dependence, and it may or may not involve a non-negligible frequency-independent leakage resistivity, pc = Pdc = po= 1/ob- There may be cases where separate processes lead to the simultaneous presence within an experimental frequency range of both types of dispersion, but this is rare for most solid electrolytes. Further complications are present when conduction involves both mobile ionic and electronic charges, neither of whose effects are negligible (Jamnik [2003]). Here only ionic, dipolar, and vibronic effects will be further considered, with the main emphasis on conductive rather than on dielectric dispersion. 

Figure 21 shows results for the frequency dependence of the ac conductivity, for E1.5B1H at several temperatures. As expected, and obtained by extrapolation to zero frequency, increase with increasing temperature. However, a discontinuity is observed in the spectra with a large step between 303 and... 

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