Electromigration of copper in lead

The electromigration of copper in lead was measured under isothermal conditions by a steady-state method. ⁶⁴Cu was introduced into the lead solvent as a radioactive tracer solute. After electromigration, the steady-state, concentration-distance curve was determined by standard sectioning, weighing and counting techniques. Although the experiments extend from 215 to 303°C, the measurements for Z¹, the effective charge number for copper in lead, appear to show at low temperature a strong dependence on concentration and are also difficult to reproduce satisfactorily in this temperature range. Accordingly only the results in the range from 240°C and up have been included in calculating the electromigration parameters. These results give Z¹ in the range 1.1 ± 0.3 and indicate an electrostatic charge, Z_el, of 1,8 ±0.9.