11B NMR Spectral and Nuclear Spin–Lattice Relaxation Analyses of ReB2

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• 作者：Dimitrios Koumoulis ; Christopher L. Turner ; R. E. Taylor ; Richard B. Kaner
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：February 11, 2016
• 年：2016
• 卷：120
• 期：5
• 页码：2901-2907
• 全文大小：376K
• ISSN：1932-7455

文摘

Analyses of the one-dimensional ¹¹B NMR spectra from static and MAS experiments of a polycrystalline ReB₂ sample have extracted parameters characterizing both the electric field gradient and the shielding at the boron site. In contrast to that previously assumed for AlB₂, the principal axis systems for these two interactions are not coincident in ReB₂. A brief discussion of the literature regarding spin–lattice relaxation for half-integer quadrupolar nuclei and the mathematical functions used for the extraction of relaxation time constants is presented. With radiofrequency conditions chosen to excite the central and satellite transitions, the saturation recovery spin–lattice relaxation rate of ReB₂ is better described by a single exponential rather than the Andrew–Tunstall multiexponential model for I = 3/2. In addition, relaxation measurements for ¹¹B in ReB₂ have been extended to temperatures above ambient and show a deviation from the Korringa relationship.