Conductivity, its anisotropy and changes as a manifestation of the features of the atomic and real structures of superprotonic [K1-x(NH4)x]3H(SO4)2 crystals

Single crystals of [K1-x(NH4)(x)](3)H(SO4)(2) (x >= 0.57) grown in the K3H(SO4)(2)(NH4)(3)H(SO4)(2)-H2O water-salt system are studied. The atomic structure including H atoms was determined at room temperature using X-ray structural analysis. [K1-x(NH4)(x)](3)H(SO4)(2) (x >= 0.57) crystals have trigonal symmetry and disordered hydrogen-bond networks at ambient conditions similar to the hightemperature phases of K3H(SO4)(2), (NH4)(3)H(SO4)(2) and other superprotonic compounds M3H(AO(4))(2). Impedance measurements performed on single crystals show high values of conductivity characteristic for superprotonic phases. Using the methods of impedance spectroscopy and atomic force microscopy, a significant anisotropy of the conductivity of crystals has been detected. It was also shown that there is a qualitative correlation of bulk and local conductivity measured for samples of the same composition and orientation at room temperature, which is due to the peculiarities of their crystal structure.