Dielectric relaxation in porous glasses

Spatial time domain reflectometry and its application for the measurement of water content distributions along flat ribbon cables in a full‐scale levee model

“…[21] The relationship between volumetric water content and dielectric permittivity is affected by various factors such as measurement frequency, temperature, mineralogical composition, structure, texture, bulk density and chemical composition of the pore fluid [Shen et al, 1987;Ishida et al, 2000;Boyarskii et al, 2002;Gutina et al, 2003;Hilhorst et al, 2001;Topp et al, 1980;Logsdon, 2005]. Therefore, the objective of numerous experimental, numerical and theoretical investigations is the development of general calibration rules for a broad range of soil textures and structures [Wang and Schmugge, 1980;Topp et al, 1980;Roth et al, 1990Roth et al, , 1992Jacobsen and Schjønning, 1993;Friedman, 1998].…”

Dielectric characteristic of nanocrystalline Na0.5K0.5NbO3 ceramic green body

“…However, unlike the Debye relaxation of pure ice, the relaxation in the green body demonstrates a nonDebye dependence, which can be connected to variance of the morphology of pores and the interaction of water molecules with the pores surface [16]. A similar dielectric relaxation behavior in silica-water systems at low water content was observed and ascribed to reorientation of water molecules in ice-like structure [17][18][19]. Therefore, the first process should arise from the same relaxation mechanism.…”

“…Finally, the low-frequency ac-conductivity σ ac demonstrates an S-shape dependency with the increase of temperature (Fig. 5), which is typical for percolation [17][18][19]. So this dielectric relaxation process results from percolation of the apparent dipole moment excitation within the developed fractal structure of the connected pores [17,18] This excitation is associated with the self-diffusion of the charge carriers in the porous net.…”

“…The liquid phase is represented by water molecule and the gaseous phase by air. Similar to porous silica glasses [16][17][18][19], water can be easily adsorbed by Fig. 1 XRD pattern of Na 0.5 K 0.5 NbO 3 nanopowder nanocrystalline particle because many defects exist on the surface of nanoparticle, furthermore, K + and Na + ions have strong hygroscopic in NKN.…”

Properties of porous glasses with embedded ferroelectric materials

“…The obtained porous glasses contained about 90% of SiO 2 ; their basic parameters relevant to the present article are given in Table 1. Our earlier investigations indicated the presence of ultrapores in PG2's silica matrix created after the chemical and temperature treatment of the original glass [8].…”