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Phase equilibria, defect ordering and ionic conductivity in the zirconia-ytterbia-yttria system

Thesis/Dissertation ·
OSTI ID:6019384
Phase equilibria in the ZrO/sub 2/Yb/sub 2/O/sub 3/-Y/sub 2/O/sub 3/ system were studied using nitrate gel prepared oxide powders and standard x-ray diffraction analysis procedures. Results on the zirconia-rich part of the ZrO/sub 2/-Yb/sub 2/O/sub 3/ binary system indicate that ytterbia is quite similar to yttria in its stabilizing effect on zirconia. In this binary system only one binary compound was found, that being Zr/sub 3/Yb/sub 4/O/sub 12/. This phase was found to be stable to 1637 +/- 13/sup 0/C where it disorders directly to the cubic fluorite structure solid solution phase. The ZrO/sub 2/-Y/sub 2/O/sub 3/ binary system was also studied, primarily in relation to the formation and stability of any binary phases. Again, only one binary phase was found, that being Zr/sub 3/Y/sub 4/O/sub 12/, which was determined to be stable to 1382 +/- 5/sup 0/C where it disorders directly to the cubic fluorite structure solid-solution phase. Studies of the zirconia-rich part of the ZrO/sub 2/-Yb/sub 2/O/sub 3/ ternary system were done at the three isotherms 1200/sup 0/, 1400/sup 0/ and 1650/sup 0/C. At 1200/sup 0/C the binary ordered phases, Zr/sub 3/Yb/sub 4/O/sub 12/ and Zr/sub 3/Y/sub 4/O/sub 12/, were found to be completely miscible. At 1400/sup 0/C the ordered phase solid solution was found to extend along the 60 m/o ZrO/sub 2/ join from 40 m/o Yb/sub 2/O/sub 3/ to only 15 m/o Yb/sub 2/O/sub 3/ plus 25 m/o Y/sub 2/O/sub 3/. At 1650/sup 0/C, where the ordered phases are no longer stable, the system is dominated by the cubic fluorite solid solution single phase field. The ionic conductivities of specimens containing 96 m/o to 86 m/o ZrO/sub 2/ were measured from 600/sup 0/C to 1000/sup 0/C in air using the complex impedance analysis technique. For a given level of total dopant, specimens doped only with ytterbia displayed higher conductivities.
Research Organization:
Pennsylvania State Univ., University Park (USA)
OSTI ID:
6019384
Country of Publication:
United States
Language:
English

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Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
360204 -- Ceramics
Cermets
& Refractories-- Physical Properties
CHALCOGENIDES
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
DISPERSIONS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
IONIC CONDUCTIVITY
MIXTURES
OXIDES
OXYGEN COMPOUNDS
PHASE STUDIES
PHYSICAL PROPERTIES
RARE EARTH COMPOUNDS
SOLID SOLUTIONS
SOLUTIONS
TRANSITION ELEMENT COMPOUNDS
VERY HIGH TEMPERATURE
YTTERBIUM COMPOUNDS
YTTERBIUM OXIDES
YTTRIUM COMPOUNDS
YTTRIUM OXIDES
ZIRCONIUM COMPOUNDS
ZIRCONIUM OXIDES