The charge storage capacity of all-glass heterogeneous materials based on phosphate and vanadate glasses

A series of compact materials has been prepared from two components: an ionically conducting (via Ag+ ions) 30AgI·35Ag2O·35P2O5 glass (denoted as I) and an electronically conducting 90V2O5·10P2O5 glass (denoted as E). They were ground and sieved in order to separate three fractions varying in grain size: 90 ÷ 100 μm, 60 ÷ 90 μm and 32 ÷ 60 μm. The powdered components were mixed in 1:1 volume ratio and pelletized under pressure. As a result, a series of heterogeneous mixed conductors has been obtained. The aim of the study was to establish a correlation between their microstructure (namely grain size) and electrical properties with a particular focus on their charge storage ability. X-ray diffractometry and DSC analyses confirmed the amorphousness of the investigated materials. Electrical properties were investigated by means of DC Hebb-Wagner polarization method and galvanostatic cycling. It was observed that the stored charge increased with the decrease of grain size. It was concluded that the charge storage ability is a synergy effect - a new feature arising from the presence of contact zones between grains of E and I glasses. Possible explanations of this effect were analyzed as well as some preliminary tests were done to evaluate the usefulness of E:I = 1:1 system as an electrode for all-solid capacitor.