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 alloys. Solute segregation at C/M interfaces is induced by intermediate-temperature 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 complemented in the MgO/Cu (Ag) system by a composition analysis of this interface employing electron energy loss spectroscopy (EELS). Analyses of 15 (222) MgO/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 degrees C. Analyses of three (222) CdO/Ag (Au) interfaces show an average segregation level of (3.0 +/- 1.0) x 10(14) atoms/cm(2) or 0.22 +/- 0.07 effective monolayers at 400 degrees C. Whereas (222) CdO/Ag (Au) interfaces in unannealed specimens show no evidence of gold segregation. These results are discussed in view of recent models of interfacial segregation. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd All rights reserved.