Pretransition Phenomena in Fast-Proton Conductors

The proton transfer along hydrogen-bonded channels has been recognized to be responsible for the charge conduction in many organic and biological systems [1–3]. Proton conducting solids are also of interest because of their potential use in fuel cells [4, 5]. Current interest to fast-proton conductors needs their synthesis, parameterization, and especially understanding of charge transport mechanism on molecular level. Since the basic work of Antonchenko, Davydov and Zolotaryuk (ADZ) [6] it has been widely believed that protons in hydrogen-bonds move in deformed double-well potential resulting from proton–lattice interactions. Combined with proton–proton interaction this characteristic provides the essential ingredients for the ionic defects to move as topological solitons. The main aim of our work is to check experimentally a validity of data description in the framework of ADZ model. To get reproducible data we have collected a number of EPR and dc current flow data for K3H(SO4)2 (KHS) fastproton conductor pure and with Mn, CrO3− 4 paramagnetic ions in the temperature region below the transition to paraelectric fast-proton conducting phase (Tg = 471 K). We were motivated by Dolinšek et al. [7] NMR work where for Rb3H(SO4)2 so-called “pretransition phenomena” were observed about 100 K below Tg. In such a way we avoided the sample decomposition and could repeat the experiments for ∗corresponding author; e-mail: [email protected]