Anisotropic Diffusion of Silver and Indium Tracers in Zinc Single Crystals

Abstract

The sectioning technique was used to measure the anisotropic diffusion of tracers in zinc single crystals. The diffusion of silver-110 was measured over the temperature range from 271° to 413°C. Referring the diffusion constants to the direction of the hexagonal symmetry axis of the zinc crystal structure, the results are: $D_{\mathrm{II}}=(0.32\mathrm{}\pm 0.02)\exp [-(26.0\mathrm{}\pm 0.1)\times {10}^3/RT] {\mathrm{cm}}^2/sec,$ $D_{\perp }=(0.45\mathrm{}\pm 0.07)\exp [-(27.6\mathrm{}\pm 0.2)\times {10}^3/RT] {\mathrm{cm}}^2/sec.$ The diffusion of indium-114 was measured over the range from 171°C to 416°C. The results are: $D_{\mathrm{II}}=(0.062\mathrm{}\pm 0.008)\exp [-(19.1\mathrm{}\pm 0.1)\times {10}^3/RT] {\mathrm{cm}}^2/sec,$ $D_{\perp }=(0.14\mathrm{}\pm 0.02)\exp [-(19.6\mathrm{}\pm 0.1)\times {10}^3/RT] {\mathrm{cm}}^2/sec.$ These show that silver diffuses at a rate about one-tenth that of zinc self-diffusion while the indium diffuses at a rate about ten times as great. Also, $D_{\mathrm{II}}>D_{\perp }$ for the silver diffusion as it is for zinc self-diffusion, while for the indium diffusion, $D_{\perp }>D_{\mathrm{II}}$. These results are interpreted to indicate a vacancy mechanism of tracer migration with the possibility of a strong tracer-vacancy association occurring in the case of the indium.