Surface segregation and oxidation studies of Cu-Sn and Cu-Pd alloys by x-ray photoelectron and auger spectroscopy

Kumar, TS Sampath and Hegde, MS (1985) Surface segregation and oxidation studies of Cu-Sn and Cu-Pd alloys by x-ray photoelectron and auger spectroscopy. In: Applications of Surface Science, 20 (3). pp. 290-306.

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Abstract

X-ray photoelectron and Auger spectroscopic techniques have been employed to study surface segregation and oxidation of Cu-1 at%Sn, Cu-9at%Pd and Cu-25at%Pd alloys. Both Cu-Pd(9%) and Cu-Pd(25%) alloys show segregation of Cu when heated above 500 K. The Pd concentration was reduced by 50% at 750 K compared to the bulk composition; the enthalpy of segregation of Cu is around - 6kJ/mol. Sn segregation is seen from 470 to 650 K in the Cu-Sn(1%) alloy, and a saturation plateau of Sn concentration above 650 K is observed. Surface oxidation of Cu-Sn(1%) and Cu-Pd(9%) alloys at 500 K showed the formation of Cu2O on the surface with total suppression of Sn or Pd on the respective alloy surfaces. On vacuum annealing the oxidised Cu-Sn alloy surface at 550 K, a displacement reaction 2Cu2O+Sn→4Cu+SnO2 was observed. However, under similar annealing of the oxidised Cu-Pd(9%) alloy surface at 500 K, oxide oxygen was totally desorbed leaving the Cu-Pd alloy surface clean. In the case of the Cu-Pd(25%) alloy, only dissociatively chemisorbed oxygen was seen at 500 K which desorbed at the same temperature. Oxygen spill-over from copper to palladium is suggested as the mechanism of oxygen desorption from the oxidised Cu-Pd alloy surfaces.

Item Type:	Journal Article
Publication:	Applications of Surface Science
Publisher:	Elsevier Science
Additional Information:	copyright of this article belongs to Elsevier Science.
Department/Centre:	Division of Chemical Sciences > Solid State & Structural Chemistry Unit Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	30 Nov 2009 09:06
Last Modified:	19 Sep 2010 05:40
URI:	http://eprints.iisc.ac.in/id/eprint/22132

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