Transformation of Tetragonal Zirconia Polycrystals by Annealing under Humidity Controlled Conditions

Tsugio Sato, Shiro Ohtaki, Tadashi Endo, Masahiko Shimada

    Research output: Contribution to journalArticlepeer-review

    2 Citations (Scopus)

    Abstract

    Changes in the crystalline phase and microstructure on the surface resulting from low-temperature annealing of tetragonal zirconia polycrystals doped 2, 3 and 4 mol%Y203 were investigated under humidity controlled conditions at 0—7. 35 kPa of water vapor pressure and 100—600°C for 1—50 hr. The tetragonal phase Zr02 transformed to the monoclinic structure by annealing at low temperature conditions such as 100—500°C. The phase transformation caused microcracks on the surface and resulted in significant loss of fracture strength. The critical temperatures of the phase transformation of Zr02-2 mol%Y203, Zr02-3 mol%Y203 and Zr02-4 mol%Y2O3 were 500, 400 and 350°C, respectively. The phase transformation proceeded rapidly on the surface but quite slowly inside the body. The rate of the phase transformation on the surface was first order with respect to the concentration of the tetragonal Zr02 and increased with increasing water vapor pressure by Langmuir type relation. The appearent activation energy of the phase transformation was about 85 kJ/mol.

    Original languageEnglish
    Pages (from-to)7-11
    Number of pages5
    JournalJournal of the Society of Materials Science, Japan
    Volume36
    Issue number400
    DOIs
    Publication statusPublished - 1987

    ASJC Scopus subject areas

    • Materials Science(all)
    • Condensed Matter Physics
    • Mechanics of Materials
    • Mechanical Engineering

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