Structural transformations and proton conductivity of Me4NHSO4 and nanocomposites Me4NHSO4 - SiO2

Abstract

The study is devoted to the quaternary ammonium compounds - Me₄NHSO₄. The detailed analysis of the proton conductivity and structural transformations of Me₄NHSO₄ in a wide temperature range was carried out firstly. A phase transition of Me₄NHSO₄ at 120°С associated with the appearance of intermediate phase with some orientational disorder of sulfate tetrahedra was observed. The slow rate phase transition at 210 °C to a high-temperature phase was firstly observed. Presumably the high-temperature phase corresponds to a tetragonal syngony. The temperature dependence of the proton conductivity fully corresponds to the structural phase transitions with the significant change of the activation energy at 120 °C from 1.8 eV to 0.7 eV up to 250 °C. The proton conductivity of Me₄NHSO₄ of the high temperature phase is an order of magnitude higher than that of the related Et₄NHSO₄ compound and reaches 4*10⁻⁴ S/cm at 250 °C. The electrotransport and structural characteristics of Me₄NHSO₄ and dispersed silicon dioxide containing composites were also investigated. The investigated (1-x)Me₄NHSO₄–xSiO₂ composites (x = 0.5 and 0.7) are characterized by the different degree of salt amorhpization and the conductivity increase.