Proton conduction study of a new selenate-based hybrid compound

Ongoing studies aimed at developing a novel proton conducting solids, resulted in the new organic-inorganic compound [(C2H5)4N] HSeO4 (H2SeO4)2. The crystals were prepared by slow evaporation technique at room temperature. Crystal structure, thermal and electrical measurements were provided to characterize this compound. Single-crystal X-ray study showed that the new phase crystallizes belongs to the Cc space group of the monoclinic system with lattice parameters: a = 19.705 (1) Å; b = 7.5420 (3) Å; c = 19.199 (1) Å, β = 115°. The structure consists of infinite two-dimensional inter-linkers via strong hydrogen bonds (O–H⋯O) giving birth to trimers. Two phase transition were disclosed by differential thermal analysis and confirmed by electrical measurements and dielectric measurements. The complex impedance of the compound was investigated in the temperature range 290–373 K and in the frequency range 1-13.103 KHz. Besides, an electrical equivalent circuit was proposed to explain the impedance results. Electric and dielectric analyses reveal the presence of a relaxation phenomenon and highlight the good protonic conduction of this material. Protons migration can be ascribed to the reorientation of protons carriers through hydrogen bonds, and then it occurs by the Grotthuss mechanism. [Display omitted] •The new organic-inorganic compound [(C2H5)4N] HSeO4 (H2SeO4)2 crystallizes in the Cc space group of the monoclinic system.•Thermal measurements allowed marking two phase transitions which are confirmed by the electrical and dielectric analysis.•The transport process occurs from the jumping of H+ protons between SeO4 groups and proton conduction can be ascribed to the transfer through hydrogen bonds and movements of charge carriers.