Degradation during aging of transformation-toughened ZrO/sub 2/-Y/sub 2/O/sub 3/ materials at 250/sup 0/C

Journal Article · Sat Mar 01 04:00:00 EST 1986 · J. Am. Ceram. Soc.; (United States)

OSTI ID:5684975

Lange, F F; Dunlop, G L; Davis, B I

The detrimental aging phenomenon observed in ZrO/sub 2/-Y/sub 2/O/sub 3/ materials, which causes tetragonal ZrO/sub 2/ to transform to its monoclinic structure at temperatures between 150 and 400/sup 0/C, was investigated with respect to the gaseous aging environment and the Y/sub 2/O/sub 3/ and SiO/sub 2/ content of the material. It is shown that the aging phenomenon is caused by water vapor and that intergranular silicate glassy phases play no significant role. Transmission electron microscopy of thin foils, before and after aging, showed that the water vapor reacted with yttrium in the ZrO/sub 2/ to produce clusters of small (20 to 50 nm) crystallites of ..cap alpha..-Y(OH)/sub 3/. It is hypothesized that this reaction produces a monoclinic nucleus (depleted of Y/sub 2/O/sub 3/) on the surface of an exposed tetragonal grain. Monoclinic nuclei greater than a critical size grow spontaneously to transform the tetragonal grain. If the transformed grain is greater than a critical size, it produces a phenomenon and results in catastrophic degradation. Degradation can be avoided if the grain size is less than the critical size required for microcracking.

• Research Organization: Structural Ceramics, Rockwell International Science Center, Thousand Oaks, CA 91360
• DOE Contract Number: FG03-84ER45124
• OSTI ID: 5684975
• Journal Information: J. Am. Ceram. Soc.; (United States), Journal Name: J. Am. Ceram. Soc.; (United States) Vol. 69:3; ISSN JACTA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202 -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
360203* -- Ceramics
Cermets
& Refractories-- Mechanical Properties
AGING
CERAMICS
CHALCOGENIDES
CRACK PROPAGATION
CRYSTAL STRUCTURE
ELECTRON MICROSCOPY
FLUIDS
FOILS
GASES
GRAIN SIZE
HIGH TEMPERATURE
MICROSCOPY
MICROSTRUCTURE
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
SILICATES
SILICON COMPOUNDS
SILICON OXIDES
SIZE
TRANSITION ELEMENT COMPOUNDS
TRANSMISSION ELECTRON MICROSCOPY
VAPORS
WATER VAPOR
YTTRIUM COMPOUNDS
YTTRIUM OXIDES
ZIRCONIUM COMPOUNDS
ZIRCONIUM OXIDES