Phase diagram and oxygen-ion conductivity in the Y2O3-Nb2O5 system

Jin Ho Lee, Masatomo Yashima, Masato Kakihana, Masahiro Yoshimura

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21 Citations (Scopus)


The phase equilibria in the Y2O3-Nb2O5 system have been studied at temperatures of 1500° and 1700°C in the compositional region of 0-50 mol % Nb2O5. The solubility limits of the C-type Y2O3 cubic phase and the YNbO4 monoclinic phase are 2.5 (±1.0) mol% Nb2O5 and 0.2 (±0.4) mol% Y2O3, respectively, at 1700°C. The fluorite (F) single phase exists in the region of 20.1-27.7 mol% Nb2O5 at 1700°C, and in the region of 21.1-27.0 mol% Nb2O5 at 1500°C, respectively. Conductivity of the Y2O3-x mol% Nb2O5 system increases as the value of x increases, to a maximum at x = 20 in the compositional region of 0 ≤ x ≤ 20, as a result of the increase in the fraction of F phase. In the F single-phase region, the conductivity decreases in the region of 20-25 mol% Nb2O5, because of the decrease in the content of oxygen vacancies, whereas the conductivity at x = 27 is larger than that at x = 25. The conductivity decreases as the value of x increases in the region of 27.5 ≤ x ≤ 50, because of the decrease in the fraction of F. The 20 mol% Nb2O5 sample exhibits the highest conductivity and a very wide range of ionic domain, at least up to log po2 = -20 (where po2 is given in units of atm), which indicates practical usefulness as an ionic conductor.

Original languageEnglish
Pages (from-to)894-900
Number of pages7
JournalJournal of the American Ceramic Society
Issue number4
Publication statusPublished - 1998 Apr

ASJC Scopus subject areas

  • Ceramics and Composites
  • Materials Chemistry

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