New superprotonic crystals with dynamically disordered hydrogen bonds: cation replacements as the alternative to temperature increase

摘要

Investigations of new single crystals grown in the K3H(SO4)(2)(-) (NH4)(3)H(SO4)(2)H2O system from solutions with different K:NH4 concentration ratios have been carried out. Based on the X-ray diffraction data, the atomic structure of the crystals was determined at room temperature taking H atoms into account. It has been determined that [K-0.43(NH4)(0.57)](3)H(SO4)(2) crystals are trigonal at ambient conditions such as the superprotonic phase of (NH4)(3)H(SO4)(2) at high temperature. A distribution of the K and N atoms in the crystal was modelled on the basis of the refined occupancies of K/N positions. Studies of dielectric properties over the temperature range 223-353 K revealed high values of conductivity of the crystals comparable with the conductivity of known superprotonic compounds at high temperatures, and an anomaly corresponding to a transition to the phase with low conductivity upon cooling.