Atomic-scale structure and chemistry of ceramic/metal interfaces - II. Solute segregation at MgO/Cu (Ag) and CdO/Ag (Au) interfaces

The first quantitative measurements of solute segregation at ceramic/metal (C/M) heterophase interfaces are presented for the MgO/Cu (Ag) and CdO/Ag ( Au) systems. Interfaces are produced by internal oxidation of ternary alloy s. Solute segregation at C/M interfaces is induced by intermediate-temperat ure annealing treatments. The Gibbsian interfacial excess of solute, Gamma( solute), at these interfaces is determined in a direct, quantitative manner by atom-probe field-ion microscopy (APFIM). These measurements are complem ented in the MgO/Cu (Ag) system by a composition analysis of this interface employing electron energy loss spectroscopy (EELS). Analyses of 15 (222) M gO/Cu (Ag) interfaces by APFIM show an average segregation level of (4.0 +/ - 1.9) x 10(14) atoms/cm(2) or 0.22+/-0.10 effective monolayers at 500 degr ees C. Analyses of three (222) CdO/Ag (Au) interfaces show an average segre gation level of (3.0 +/- 1.0) x 10(14) atoms/cm(2) or 0.22 +/- 0.07 effecti ve monolayers at 400 degrees C. Whereas (222) CdO/Ag (Au) interfaces in una nnealed specimens show no evidence of gold segregation. These results are d iscussed in view of recent models of interfacial segregation. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd All rights reserved.