nuclear magnetic resonance detection of diffusion processes in ) and

Abstract

The alloy system has been investigated by means of NMR around the equiatomic region where x = 0.5, and at x = 0.6, which gives the trigonal ordered compound . For , two Al sites were clearly resolved at room temperature by means of their characteristic second-order quadrupolar structure. NMR spectra for cubic taken at temperatures up to show rapid line narrowing above for x = 0.54 (indicative of diffusion processes), but no such line narrowing was observed up to for x = 0.50 or x = 0.48. NMR results are also reported for the equiatomic alloy. For , the NMR powder pattern evolved smoothly into that characteristic of one well defined site as the temperature was raised to , although no phase transition was detected by means of powder x-ray diffraction or thermal analysis. These observations are discussed qualitatively in terms of defect-assisted diffusion processes.

Recent progress in solid‐state nuclear magnetic resonance of half‐integer spin low‐γ quadrupolar nuclei applied to inorganic materials

“…61 Ni highfield NMR approaches first reported NiAl where a shift of 1220 ppm from the diamagnetic nickel position was observed due to Knight shift effects. [211] This was followed up by a report on a more extensive range of binary intermetallics (NiAl, NiGa, NiIn) showing an increase in the 61 Ni Knight shift from aluminium to gallium to indium. [212] The only other 61 Ni solid-state NMR from a diamagnetic nickel(0) species has been for a series of coordination organometallic complexes.…”

Characterization of Anisotropic Aluminum Magnetic Shielding Tensors. Distorted Octahedral Complexes and Linear Molecules

“…At the same time, our group had submitted a report of a relatively large 27 Al CSA in aluminum trichloride phosphoryl trichloride, AlCl 3 ·OPCl 3 . Aside from these examples of aluminum CSA, the only other interaction that influences the line shape of solid-state NMR spectra in a similar fashion is the Knight shift, which has been observed in the 27 Al NMR spectra of binary aluminum−metal alloys . However, the Knight shift is only functional in conducting or semiconducting materials.…”

A Definitive Example of Aluminum-27 Chemical Shielding Anisotropy

“…The Knight shift (10) is an anisotropic interaction which may influence the line shape of a solid-state 27 Al NMR spectrum in a fashion analogous to the anisotropic CS interaction; however, it is only operative in conducting and semiconducting materials. For example, the Knight shift has been shown to be important in solid-state 27 Al NMR spectra of binary aluminum-metal alloys (11,12).…”