Solid-state NMR investigations of Si-29 and N-15 enriched silicon nitride

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