文摘
To study the reorientational motion of the anions and the translational diffusion of Na+ cations in the mixed borohydride鈥揳mide Na2(BH4)(NH2) showing fast-ion conduction, we have measured the 1H, 11B, and 23Na NMR spectra and spin鈥搇attice relaxation rates in this compound over broad ranges of temperature (6鈥?80 K) and the resonance frequency (14鈥?32.3 MHz). At low temperatures (T < 190 K), the proton spin鈥搇attice relaxation rate is governed by fast reorientations of BH4 groups. This reorientational process can be satisfactorily described in terms of a Gaussian distribution of the activation energies with the average Ea value of 74 卤 7 meV. Above 250 K, the measured proton spin鈥搇attice relaxation rate originates from two other (slower) reorientational jump processes characterized by the average activation energies of 340 卤 9 meV and 559 卤 7 meV. The 23Na spin鈥搇attice relaxation data in the high-temperature region are governed by translational diffusion of Na+ ions, which is consistent with high Na-ion conductivity in Na2(BH4)(NH2).