Nuclear Magnetic Resonance Study of Atomic Motion in the Mixed Borohydride鈥揂mide Na2(BH4)(NH2)

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• 作者：Alexei V. Soloninin ; Olga A. Babanova ; Evgeny Y. Medvedev ; Alexander V. Skripov ; Motoaki Matsuo ; Shin-ichi Orimo
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：July 10, 2014
• 年：2014
• 卷：118
• 期：27
• 页码：14805-14812
• 全文大小：388K
• ISSN：1932-7455

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 E_a 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).