Dielectric properties of metal salts of heteropolyacid hydrates

Abstract

Heteropolyacids hydrates as superionic conductors have been intensely investigated during the last fifteen years. By using various experimental techniques such as IR and Raman spectroscopy, neutron scattering, impedance measurements, X-ray diffraction and others, informations have been obtained on the properties of protonic entities and conductivity mechanisms. The salts of heteropolyacids have been less investigated although there is a steady growth of activities in this field too. In this work the results of permittivity measurements are presented on copper and calcium salts of 12-tungstophosphoric acid hydrates (CuHPW12O40. 15H(2)O and CaHPW12O40. 13H(2)O). Measurements have been done in the region of microwaves, at room temperature and in a room ambient. The aim of this work was to study the influence of copper and calcium ions on dielectric relaxation processes in these salts. Dielectric relaxations have been found for both salts. Contributions of fast reorientations of H2O molecules and oxonium ions (H3O+) to these relaxations are discussed as well as, their influence on dynamic conductivity.