Conductivity and permittivity of Type I, II and III cement pastes have been measured during the first 24 h hydration period at 10.0 GHz using the infinite sample method. Correlations between the electrical parameters and the chemical processes are discussed. Conductivity and relative permittivity are shown to be affected by the water-cement ratio and the type of cement. Changes in electrical parameters during the hydration processes coincide with hydration stages as derived from calorimetry measurements.

Conductivity and permittivity of cements were measured during the first 24 h hydration period at 10.0 GHz using front surface reflection methods. Data trends closely followed the hypothesis that the microwave results responded to the transition from free to bound water as hydration proceeded. The results were also compared to measured hydration curves and changes in the slope of the data versus time correlated well with characteristics regions of the hydration curve. The results establish the usefulness of microwave characterization for the study of chemistry and structure during the hydration period and may lead to a non destructive test method for cementitious materials during the early curing period.

Frequency dependent conductivity and dielectric constant of crystalline and amorphous phases of the polymeric solid electrolyte-(PEO)8NH4SO3CF3 were studied in the frequency range from dc to 37 GHz. The complex permittivity variation with frequency conforms to the dynamic percolation model.

Complex conductivity spectra of Ag2HgI4 in the radio and microwave frequency range reveal distinctive features separating the ionic conducting α-phase from electronic conducting β-phase. In the α-phase, a power law conductivity spectrum, a relaxation-like permittivity spectrum, together with thermal activation effects, are indicative of hopping transport with a distribution of hopping times. Single-particle kinetics are thought to play a dominant role in the long time scale since many of the observed structures can be explained by a model based on jump diffusion. In the β-phase, a non-dispersive permittivity and the lack of thermal activation effects suggest that the observed response is the long-wavelength tail of an infrared vibrational mode.

The cation order-disorder phase transition of Ag2HgI4 and Cu2HgI4 involves a major change only in the cation sublattice and is accompanied by a jump in the dc conductivity. Critical dynamics of this phase transition have been studied by microwave conductivity measurement. When the frequency of excitation is high enough, an extra critical structure with no correspondence to dc conductivity is revealed. It is plausible that the transition is driven by coupling between the cations themselves as there is very little difference in the I− sublattice before and after the transition. The close resemblance to a ferroelectric leads to the suggestion that the anomaly is due to the renormalized vibrational mode of the cations. A phenomenological expression for the complex conductivity spectrum based on quasi-chemical and mean field theories is constructed to give a qualitative account of the experimental observation.

Dynamics of PEO·NaSCN (a solid electrolyte) and PEO·NaBH4 (an insulator) have been studied by dielectric loss measurements in the radio and microwave frequency regions. Above 10 GHz, the response is principally attributed to contributions from vibrational motions of the polymer itself. The mid frequency dielectric response of the NaSCN complex indicates a coupling between motions of the sodium ion and the polymer chain. The absence of extra low frequency polarization in the NaBH4 complex suggest that the sodium ion is held tightly to the polymer backbone,,possibly due to ion-pairing with the anion.

Polymer electrolytes based on alkali metal complexes of polyethers and cross-linked polyethers have significant cation mobility, which appears to arise from large-amplitude motions of the polymer. High chain flexibility not only promotes ion transport but it also is important for the initial formation of polymer-salt complexes. Several new polymer electrolyte systems are discussed which contain flexible polymer backbones and high concentrations of polar groups.

The complex conductivity of polycrystalline Ag 2 HgI 4 , a superionic conductor, has been measured as a function of temperature at 10, 24 and 70 GHz. Both conductivity and permittivity exhibited sharp changes at the β↔α phase transition. The microwave conductivity of the β-phase was found to be insensitive to temperature changes and that of the α-phase has thermal activation energies lower than that of dc. The observed monotonic increasing conductivity, decreasing permittivity, together with thermal activation effects are indicative of hopping ionic transport.

The dielectric relaxation associated with hopping ionic conduction is investigated within the context of the jump diffusion model with classical activation over a barrier. Expressions relating conductivity and permittivity to lattice parameters and temperature are obtained. A superposition of Debye relaxations leads to a conductivity increasing with frequency and a permittivity which decreases with frequency. The theoretical formulation yields a realistic description of ionic motion in the dc limit.