Anisotropy of the Snoek Phenomenon in Niobium

Abstract

The anisotropy of the strength of the Snoek relaxation has been measured for both oxygen and nitrogen in niobium. Single crystals of niobium of extreme orientations, [100] and [111], as well as several intermediate orientations were grown in an electron beam melter. The height of the Snoek peaks of the residual oxygen and nitrogen was measured at 80 kcps using a quartz transducer. The orientation for which the peak height is maximum is [100]; the orientation for which it is minimum is [111] —it is actually zero for this orientation. This result shows that the interstitial site is symmetrical about [111], but it alone does not differentiate between occupancy by the interstitial of the octahedral and tetrahedral sites.