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M: Metallphysik

M 36: Diffusion und Punktdefekte I

M 36.1: Vortrag

Donnerstag, 27. März 2003, 10:15–10:30, IFW B

Segregation Behavior of Ge and Bi in Cu: Grain Boundary Diffusion Measurements in B and C Kinetic Regimes — •Maik Lohmann¹, Sergiy Divinski¹, Brigitte Baretsky², and Christian Herzig¹ — ¹Institut für Materialphysik, Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany — ²Max-Plank-Institut für Metallforschung, Heisenberstr. 3, 70569 Stuttgart, Germany

Ge and Bi grain boundary (GB) diffusion in high-purity Cu was measured by the radiotracer method. At higher temperatures the conditions of Harrison’s B kinetics were satisfied that allowed to determine the product P=s·δ· D_gb of the segregation factor s, GB width δ, and the GB diffusivity D_gb. Performing GB diffusion measurements at lower temperatures under the C regime conditions, the GB diffusion coefficient D_gb was directly determined. Using the well-known estimates of the GB width δ∼5·10⁻¹⁰m, the temperature dependence of the segregation factor is given by s=P/δ D_gb. The segregation enthalpies of Ge and Bi in Cu were found to be −26 and −53 kJ/mol, respectively. While Ge reveals only moderate segregation level (s_Ge∼120 at T=500K), Bi is a very strong segregant in Cu with the segregation factor s_Bi of about 2·10⁴ at T=500K.