Subnanometer three-dimensional atom-probe investigation of segregation at MgO/Cu ceramic/metal heterophase interfaces

Three-dimensional atom-probe (3DAP) microscopy has been applied to the stud y of segregation at ceramic/metal (C/M) interfaces. In this article, result s on the MgO/Cu(X) (where X = Ag or Sb) systems are summarized. Nanometersi ze MgO precipitates with atomically clean and atomically sharp interfaces w ere prepared in these systems by internal oxidation. Segregation of the ter nary component (Ag or Sb) at the MgO/Cu heterophase interface was enhanced by extended low-temperature anneals. Magnesia precipitates in the 3DAP reco nstructions were delineated as isoconcentration surfaces, and segregation o f each ternary component at the C/M interfaces was analyzed with the proxim ity histogram method developed at Northwestern University. This method allo ws the direct extraction of the Gibbsian interfacial excess of solute at th e C/M interfaces from the experimental data. A value of (3.2 +/- 2.0) x 10( 17) m(-2) at 500 degreesC is obtained for the segregation of Ag at a MgO/Cu (Ag) interface, while a value of (2.9 +/- 0.9) x 10(18) m(-2) at 500 degree sC is obtained for the segregation of Sb at a MgO/Cu(Sb) interface. The lar ger Gibbsian excess for Sb segregation at this ceramic/metal heterophase in terface is most likely due to the so-called p DeltaV effect. (C) 2001 Elsev ier Science B.V. All rights reserved.