Effect of monovalent cation additives on the γ-Al2O3-to-α-Al2O3 phase transition

Kiyoshi Okada, Akiyoshi Hattori, Yoshikazu Kameshima, Atsuo Yasumori, Rathindra Nath Das

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Abstract

The effect of monovalent cation addition on the γ-Al2O3-to-α-Al2O3 phase transition was investigated by differential thermal analysis, powder X-ray diffractometry, and specific-surface-area measurements. The cations Li+, Na+, Ag+, K+, Rb+, and Cs+ were added by an impregnation method, using the appropriate nitrate solution. β-Al2O3 was the crystalline aluminate phase that formed by reaction between these additives and Al2O3 in the vicinity of the γ-to-α-Al2O3 transition temperature, with the exception of Li+. The transition temperature increased as the ionic radii of the additive increased. The change in specific surface area of these samples after heat treatment showed a trend similar to that of the phase-transition temperature. Thus, Cs+ was concluded to be the most effective of the present monovalent additives for enhancing the thermal stability of γ-Al2O3. Because the order of the phase-transition temperature coincided with that of the formation temperature of β-Al2O3 in these samples, suppression of ionic diffusion in γ-Al2O3 by the amorphous phase containing the added cations must have played an important role in retarding the transition to α-Al2O3. Larger cations suppressed the diffusion reaction more effectively.

Original languageEnglish
Pages (from-to)1233-1236
Number of pages4
JournalJournal of the American Ceramic Society
Volume83
Issue number5
Publication statusPublished - Jan 1 2000

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ASJC Scopus subject areas

  • Ceramics and Composites
  • Materials Chemistry

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