Protonic conductivity of solid potassium dihydropyroantimonate

Abstract

The electrical properties of solid K 2H 2Sb 2O 7·4H 2O have been investigated in temperature range from room temperature up to 400°C. The temperature dependence of the conductivity seems to indicate a change in the nature and number of charge carriers in the sample. By means of the admittance method applied to the cell Ag/K 2H 2Sb 2O 7·4H 2O/Ag we have been able to determine certain resistance parameters of the electrolytical cell by measurement and to make some assumptions and conclusions about the nature of charge carriers and the mechanism of conductivity. By correlating the results of these investigations with thermal and structural characteristics proved by IR spectra, we suggest a mechanism of the electrical conductivity valid in a certain temperature range. From 20–250°C, the electrical conductivity is attributed to the presence of a stable network of OH - groups, formed by strong hydrogen bonds along which the proton moves. In the case of Sb(V) it is hardly possible for the metal ions to leave the octahedron structure. Consequently, metal ions do not contribute to the conductivity. Disturbance of the octahedron structure, caused by dehydration up to 200°C gives rise to a significant concentration of Sb(V) and K + ions which take part in the conduction process, together with already present OH - and H + ions.