6Li and 7Li solid-state NMR spectroscopy of nitrogen ceramic phases

✍ Scribed by Pierre Kempgens; Robin K Harris; Derek P Thompson

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 230 KB
• Volume: 15
• Category: Article
• ISSN: 0926-2040
• DOI: 10.1016/s0926-2040(99)00040-5

✦ Synopsis

Two nitrogen ceramic phases, the oxynitride LiSiON and the nitride LiSi N , have been studied by 6 Li and 7 Li NMR. 2 3 Ž . Ž . Magic angle spinning MAS NMR experiments have been carried out at two magnetic field strengths 7.05 and 14.1 T .

The spectra give evidence of the relative effects of the quadrupolar and chemical shift interactions. The electric field gradient tensor of both phases has been determined accurately by iterative fitting of the 6 Li and 7 Li MAS NMR line shapes at the two magnetic field strengths. Due to the fact that for 7 Li the quadrupolar interaction is much larger than the chemical shift interaction, it is shown that neither the small chemical shift anisotropy nor the relative orientation of the two interaction tensors can be determined accurately by 7 Li MAS NMR. For 6 Li, the two interactions are comparable and the value of these parameters obtained from the fits of the 6 Li experimental MAS line shapes are therefore much more reliable.