Electrochemical Methods for the Measurement of High‐Temperature Diffusion in Metals

Abstract

Previous determinations of the diffusion coefficient of silver in single‐crystal Ag‐Au alloys at 394° by the measurement of diffusion‐limited currents in solid electrolyte cells have been extended to cover the complete alloy composition range and to determine the effects of electrode surface preparation, direction of diffusion, compositional cycling, and use of a bulk Ag‐Au alloy as the starting electrode. In addition, the experimental and theoretical principles are discussed more thoroughly. In selected systems, the method permits the accurate measurement of D values as low as 10−16 cm2/sec, at a time scale of about 1 hr per data point, over the range of miscibility of diffusant and solute metals, with a single cell. In the present study, D values from duplicate runs in the range . The method permitted, for the first time, direct comparison of D values corresponding to inward and outward diffusion in a substitutional solid system. Out‐diffusion D values were systematically higher, a result attributed to vacancy injection. Extension of the present and related methods to fused salt electrolytes and other solid electrode materials is discussed.