Characteristic features of the molecular dynamics and phase transitions of mixed [(NH4)1−xRbx]3H(SO4)2 (x = 0, 0.8, and 1) crystals using 1H and 87Rb NMR

In this study, we grew [(NH4)1−xRbx]3H(SO4)2 (x = 0, 0.8, and 1) mixed crystals using a slow evaporation method and determined their lattice constants by X-ray diffraction. We investigated the molecular dynamics and phase transition temperatures of the crystals using 1H and 87Rb nuclear magnetic resonance (NMR) relaxation and differential scanning calorimetry. When a fraction of rubidium ions in the pure Rb3H(SO4)2 crystal is partial replaced by ammonium ions, we compared the physical properties of the three types of crystals. A small amount of NH 4 + added to Rb3H(SO4)2 led to a change in the physical properties, bringing about a shift in phase transition temperatures and showed a superprotonic phase transition.