Relaxation process due to molecular inclusions in non-crystalline solids

Abstract

The dielectric, thermodynamic and electric conduction behaviour of amorphous solids with three types of inclusions are described. In the first, or the self-inclusion in glasses, the features of dielectric relaxation due to localized rotational diffusion have a remarkable resemblance to those of the rotation of guest molecules in clathrate structures. But here, the availability of the various configurational states to molecules in the local regions makes a relatively greater contribution to the thermodynamic behaviour of a glass than is observed in clathrates. The number of such self-inclusions decreases as a glass spontaneously densifies on ageing. In this respect, the features attributable to such inclusions in a non-crystalline solid differ from those of a crystalline solid. In the second, - 20 A size inclusions or microdomains of strained a-AgI (bec lattice) are randomly distributed in AgI-AgP03 glasses. The electrical conductivity due to such inclusions follows a power law characteristic of site percolation with a percolation threshold of 0.3, critical exponent 3.3, vulnerability 4.8 and the number of contact sites 2.7. In the third, the part of the repeat unit of a randomly oriented poly(vinyl pyrrolidone) becomes incorporated as inclusions in the distorted, H-bonded, cage-like structures formed by the water molecules. The features of dielectric relaxation of water molecules in the solid aqueous solution of the polymer are similar to those of ice clathrates containing a guest molecule similar in size to pyrrolidone, but the respective temperature dependence of their rates differ.