Abstract
We compare 29Si magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectra from the two modifications of silicon nitride, α-Si 3N 4 and β-Si 3N 4, with that of a fully ( 29Si, 15N)-enriched sample 29Si 3 15N 4, as well as 15N NMR spectra of Si 3 15N 4 (having 29Si at natural abundance) and 29Si 3 15N 4. We show that the 15N NMR peak-widths from the latter are dominated by J( 29Si– 15N) through-bond interactions, leading to significantly broader NMR signals compared to those of Si 3 15N 4. By fitting calculated 29Si NMR spectra to experimental ones, we obtained an estimated coupling constant J( 29Si– 15N) of 20 Hz. We provide 29Si spin-lattice ( T 1) relaxation data for the 29Si 3 15N 4 sample and chemical shift anisotropy results for the 29Si site of β-Si 3N 4. Various factors potentially contributing to the 29Si and 15N NMR peak-widths of the various silicon nitride specimens are discussed. We also provide powder X-ray diffraction (XRD) and mass spectrometry data of the samples.
Published Version
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