Protonic conductivity and phase transition in K1 − x(NH4)xHSO4

► Solid solution K1 − x(NH4)xHSO4 becomes superprotonic at 0.1 < x < 0.8. ► The proton conduction in K1 − x(NH4)xHSO4 is contributed from two relaxation processes. ► The origin of them is considered to be the coupled reorientation of NH4+ and HSO4−.