Dielectric relaxation of porous glasses

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

“…4(a) and (b) of the first process correlates with that of pure ice [20]. 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].…”

“…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.…”

Comment on “Investigating hydration dependence of dynamics of confined water: Monolayer, hydration water, and Maxwell–Wagner processes” [J. Chem. Phys. 128, 154503 (2008)]

“…Anomalous temperature dependence is then explained by losses of hydration water at high temperatures. In this regard, one may note that all the similar systems investigated earlier [2][3][4] where this phenomenon of has been observed do not demonstrate significant changes of dielectric strength for the process with nonmonotonic relaxation kinetics over the whole temperature range. Thus, the assumption that the losses of water during the sample heating can lead to such drastic changes in relaxation kinetics is questionable.…”

“…The subject of water in confined porous matrices has been an area of our interests for about a decade. [2][3][4][5][6] Therefore, the study of Sjöström et al 1 attracted our attention and we would like to point out some questionable, from our point of view, aspects of their investigation.…”

“…In general, it is believed that the Johari-Goldstein relaxation is a precursor of glassy dynamics but no glass transition is detected in the system. In literature [2][3][4][5][6]8,9 this low temperature process is usually ascribed to the icelike behavior of water molecules.…”