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The electrical and dielectric properties of the copper salt of 12-tungstophosphoric acid (WPA) hydrate have been investigated by broadband dielectric relaxation spectroscopy (DRS). This work is a continuation of our previous investigations on the influence of monovalent and bivalent cations on the dielectric properties of WPA hydrates salts. Measurements were made in the frequency range 10 mHz–1 MHz in order to explore the long-range dynamics, following recent microwave measurements aiming at the local dynamics properties. Experiments were done in the temperature interval 293–350 K. Data treatment included complex permittivity ϵ*, complex electric modulus M* and complex impedance Z* formalism, Arrhenius diagram and Cole–Cole diagrams. The results are discussed in terms of conductivity relaxation and conductivity current relaxation. Rather long conductivity relaxation times measured seem to correspond to ion jumping processes. A phase transition was observed at 323 K. [Copyright &y& Elsevier]

Some structural properties of a magnesium salt of 12-tungstophosphoric acid, MgHPW12O40·nH2O (MgHWPA-n), are reported. The influence of the Mg2+ ion on the structure, dynamics of the protonic species, and dielectric and conductive characteristics of the salt have been studied. The interaction of protonic species with Keggin anion was discussed. Preliminary results of the crystal structure indicate that the structure is composed of Keggin anions and Mg(OH2)6 aqua-complexes. Some comparisons are made with other alkaline-earth and alkaline salts of WPA. The results of thermal analysis (TGA and DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (IR), conductivity and permittivity measurements of MgHWPA-n are reported and discussed. [Copyright &y& Elsevier]