ABSTRACT
We present the frequency study of electric conductivity in the superprotonic single crystal in a wide temperature range covering the superprotonic phase I and the low conducting, ferroelastic phase II. The data below microwave frequencies are analyzed using the Summerfield scaling method to check for presence of the first universality. The scaled conductivity obtained from the raw experimental data plotted versus scaled frequency do not show the universality because it contains, in a low temperature range, steps related to relaxational dielectric contribution. The contribution, evidenced by a temperature study of frequency dependence of εâ³, presumably comes from polar ammonia and therefore does not reflect properties of the hopping motion of mobile ions. To get rid of it, the conductivity is calculated using the impedance data obtained from the fitting procedure of the Nyquist plots. The resulting scaled ac conductivity plot forms a single curve in a wide temperature range. Thus, (NH4)3H(SO4)2 meets criteria for the first universality, despite the fact that it undergoes the structural, superionic phase transition in the temperature range studied.
ABSTRACT
The present paper describes a preparation method and molecular investigations of new biodegradable proton-conducting carbohydrate polymer films based on alginic acid and benzimidazole. Electric conductivity was studied in a wide temperature range in order to check the potential application of these compounds as membranes for electrochemical devices. Compared to pure alginic acid powder or its film, the biodegradable film of alginic acid with an addition of benzimidazole exhibits considerably higher conductivity in the range above water boiling temperature (up to approximately 10(-3) S/cm at 473 K). Due to this important feature the obtained films can be considered as candidates for application in high-temperature electrochemical devices. The microscopic nature and mechanism of the conduction in alginate based materials were studied by proton nuclear magnetic resonance (NMR). The results show specific changes in morphology and molecular dynamics between pure alginate powders and the films obtained without and with the addition of benzimidazole molecules.
