The initial stage in oxidation of ZrNiSn (half Heusler) alloy by oxygen

Oshrat Appel, Gil Breuer, Shai Cohen, Ofer Beeri, Theodora Kyratsi, Yaniv Gelbstein, Shimon Zalkind

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

The MNiSn (M = Ti; Zr; Hf); half-Heusler semiconducting alloys have a high potential for use as n-type thermoelectric materials at elevated temperatures (~1000 K). The alloys' durability is crucial for their commercial handling and use, and therefore it is required to characterize their surface oxidation behavior and stability at the working temperature. X-ray photoelectron spectroscopy was utilized to study the surface composition and oxidation of the ZrNiSn alloy at room and elevated temperatures. It was found that during heating in a vacuum, Sn segregates to the surface in order to reduce the surface energy. Exposing the alloy to oxygen resulted mainly in the oxidation of the zirconium to ZrO2, as well as some minor oxidation of Sn. At room temperature, the oxidation to ZrO2 was accompanied by the formation of a thin ZrO layer at the metal-oxide interface. In contrast to TiNiSn, where most of the oxide was formed on the surface due to oxygen-enhanced segregation of Ti, and in the case of ZrNiSn, the formed oxide layer was thinner. Part of the oxide is formed due to Zr segregation to the surface, and in part due to oxygen dissolved into the alloy.

Original languageEnglish
Article number1509
JournalMaterials
Volume12
Issue number9
DOIs
StatePublished - 1 Jan 2019

Keywords

  • Half-Heusler
  • Oxygen
  • Segregation
  • Surface oxidation
  • Thermoelectric
  • XPS
  • ZrNiSn

ASJC Scopus subject areas

  • General Materials Science

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