nuclear magnetic resonance detection of diffusion processes in ) and

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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.