High-frequency broadband dielectric spectroscopy on sugar alcohols below Tg

The dielectric spectra of sugar alcohols, sorbitol and xylitol, are studied in the frequency range (40 Hz–10 GHz) and the temperature range (140–360 K) in order to evaluate the contribution from nearly constant loss (NCL). The dielectric loss data are analyzed from the view point of both frequency dependence and temperature dependence. Although the loss spectra at far below Tg do not distinguish between contributions from the Johari–Goldstein (JG)-β process and the NCL to the high frequency dielectric loss, careful analysis of the temperature dependence reveals contribution of the NCL at very high frequencies in GHz region. This result supports the existence of NCL.