Abstract :
The temperature dependences of the line width, chemical shift, and spin–lattice relaxation time in the rotating frame, T1ρ, of the ammonium protons and hydrogen-bond protons in (NH4)4LiH3(SO4)4 are investigated by 1H MAS NMR. The change in the chemical shift for hydrogen-bond protons near the superionic phase transition TS (=405 K) indicates both H-bond breaking and new H-bond formation. Further, 1H T1ρ for the hydrogen-bond protons changes significantly near TS, and these protons play a more prominent role than the ammonium protons. Between TC (=232 K) and TS, molecular motions of the ammonium and hydrogen-bond protons occurred. The hydrogen-bond protons significantly influence the superionic phase transition of (NH4)4LiH3(SO4)4.
