Thermodynamic properties of oxygen in RE-O (RE=Gd, Tb, Dy, Er) solid solutions

T. H. Okabe, K. Hirota, E. Kasai, F. Saito, Y. Waseda, K. T. Jacob

Research output: Contribution to journalArticlepeer-review

54 Citations (Scopus)

Abstract

The oxygen potentials of four rare-earth metal - oxygen (RE-O: RE=Gd, Dy, Tb, Er) solid solutions have been measured by equilibration with yttrium - oxygen (Y-O) and titanium - oxygen (Ti-O) solid solutions. Rare-earth metal, yttrium and titanium samples were immersed in calcium-saturated CaCl2 melt at temperatures between 1093 and 1233 K. Homogeneous oxygen potential was established in the metallic samples through the fused salt, which contains some dissolved CaO. The metallic samples were analyzed for oxygen after quenching. The oxygen potentials of RE-O solid solutions were determined using either Y-O or Ti-O solid solution as the reference. This method enabled reliable measurement of extremely low oxygen potentials at high temperature (circa po2 = 10-48 atm at 1173 K). It was found that the oxygen affinity of the metals decreases in the order: Y>Er>Dy>Tb>Gd>Ti. Values for the standard Gibbs energy of solution of oxygen in RE metals obtained in this study, permit assessment of the extent of deoxidation that can be achieved with various purification techniques. It may be possible to achieve an oxygen level of 10 mass ppm using an electrochemical deoxidation method.

Original languageEnglish
Pages (from-to)184-191
Number of pages8
JournalJournal of Alloys and Compounds
Volume279
Issue number2
DOIs
Publication statusPublished - 1998 Oct 2

Keywords

  • Deoxidation
  • Dysprosium
  • Erbium
  • Gadolinium
  • Gibbs energy
  • Rare-earth metals
  • Solution of oxygen
  • Terbium
  • Thermodynamics
  • Yttrium

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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