Electrical Resistivities of Single and Optically Mosaic Zinc Crystals

Abstract

The Voigt-Thomson symmetry relation is accurately checked for two sets of strain-free zinc single crystals made from two lots of Evanwall zinc. The principal electrical resistivities in micro-ohms/${\mathrm{cm}}^{3}$ are: ${\ensuremath{\rho}}_{0}=6.218$, ${\ensuremath{\rho}}_{90}=5.882$ with the ratio, $\frac{{\ensuremath{\rho}}_{0}}{{\ensuremath{\rho}}_{90}}=1.0554$ for one lot (E.W.R.) and ${\ensuremath{\rho}}_{0}=6.161$, ${\ensuremath{\rho}}_{90}=5.842$, $\frac{{\ensuremath{\rho}}_{0}}{{\ensuremath{\rho}}_{90}}=1.0548$ for the other (E.W.B.). The resistivity is changed by slight strains due to application of micrometer calipers to the crystals, the change being a decrease in four cases out of eleven. Severe strains, in general, increase the resistivity. The effects of repeated anneals on strained crystals are complex, the most important conclusion being that high temperature anneals (at about 400\ifmmode^\circ\else\textdegree\fi{}C) are not effective in restoring the initial resistivity of all orientations. A final low temperature anneal (at 190\ifmmode^\circ\else\textdegree\fi{}C for 84 hours) is however completely effective. Optically mosaic specimens have abnormal resistivities, either greater or less than single crystals of the same orientation. Such specimens are very strain-sensitive, the resistivity rising markedly after a strain and falling for a subsequent anneal. This effect may be repeated several times on a specimen. The ambiguous results of previous observers may be explained either as strain effects or as due to the presence of optically mosaic specimens.