Dielectric relaxed/unrelaxed

The best evidence so far for the glassy nature of HDA was provided (1) by measurements of the dielectric relaxation time under pressure at 140 K [206, 251], (2) by the direct vitrification of a pressurized liquid water emulsion to HDA [252], and (3) by a high-pressure study of the glass >liquid transition using differential thermal analysis (DTA) [253], We note here that these studies probe structurally relaxed HDA (eHDA) rather than unrelaxed HDA. It is possible that structurally relaxed HDA behaves glass like, whereas structurally uHDA shows a distinct behavior. Thus, more studies are needed in the future, which directly compare structurally relaxed and unrelaxed HDA. 

Interfacial or Maxwell-Wagner polarization is a special mechanism of dielectric polarization caused by charge build-up at the interfaces of different phases, characterized by different permittivities and conductivities. The simplest model is the bilayer dielectric [1,2], (see Fig. 1.) where this mechanism can be described by a simple Debye response (exponential current decay). The effective dielectric parameters (unrelaxed and relaxed permittivities, relaxation time and static conductivity) of the bilayer dielectric are functions of the dielectric parameters and of the relative amount of the constituent phases ... 

In Equation 1, R and V refer to the relaxed (low frequency) and unrelaxed (high frequency) dielectric constants, and AH is the measured activation energy for the y process. The latter was nearly independent of blend composition an average value of 8.7 kcal/mole was used. The integral in Equation 1 was found to be approximately independent of frequency in the range studied. The loss peak in absolute terms is rather weak, and values of eR — V were of the order of 10"2 and less. From these values, it was also possible to calculate the apparent dipolar density, Np2, using the Onsager relation (9) ... 

The dielectric equivalent of Eq. (12.16) relates s to the relaxed low frequency dielectric constant r and the unrelaxed high frequency value u... 

The terms relaxed and unrelaxed dielectric constant are used for the static and high-frequency values e and respectively. These quantities... 

Here a is the bulk ionic or dc conductivity is the angular frequency (27rf) r is the dipole relaxation time is the relaxed dielectric constant or low frequency/high temperature dielectric constant (relative permittivity due to induced plus static dipoles) is the unrelaxed dielectric constant or high frequency/low temperature dielectric constant (relative permittivity due to induced dipoles only) o is the permitivity of free space E p is the electrode polarization term for permittivity and E"-p is the electrode polarization term for loss factor. The value of E p and E"p is usually unity, except when ionic conduction is very high (75). 

Where As= Ss- s, Sao and Ss are the unrelaxed and relaxed values of the dielectric constant, Thn is a characteristic relaxation time, and b and c are shape parameters (0 < Z>, c < 1) which describe the symmetric and the asymmetric broadening of the equivalent relaxation time distribution function,... 

---