Ionic conductivity in the hafnia-rare earth systems and phase equilibria in the system hafnia-zirconia-yttria
Phase equilibria in the system hafnia-zirconia-yttria were investigated at 1300/sup 0/C and 1600/sup 0/C by precise lattice-parameter measurements and the direct phase-inspection method. Large fluorite solid solution regions are dominant at both investigated temperatures. The extent of ordering within the ternary was studied in the samples containing 40 m/o yttria at 1300/sup 0/C. The delta-phase ((Zr,HF)/sub 3/Y/sub 4/O/sub 12/) formation was established only in those samples with less than 15 m/o hafnia content. Nonequilibrium behavior was found in the samples containing the yttria-based C-type rare-earth solid-solution phase. The bulk ionic conductivity of the hafnia-rare earth fluorite-type solid solutions was measured on the samples prepared by co-precipitation of chloride solutions, using the impedance spectroscopy technique. The conductivities of the hafnia-rare earth systems was generally found to be approx. 2-5 times lower than those reported previously for the corresponding zirconia-based systems. A maximum in the ionic conductivity, accompanied by a minimum in the activation energy of conduction, was observed near the 10 m/o dopant concentration for the yttria, ytterbia, and samaria-doped samples.
- Research Organization:
- Pennsylvania State Univ., University Park (USA)
- OSTI ID:
- 7005136
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
HAFNIUM OXIDES
PHASE STUDIES
SOLID SOLUTIONS
SAMARIUM OXIDES
IONIC CONDUCTIVITY
YTTERBIUM OXIDES
YTTRIUM OXIDES
ZIRCONIUM OXIDES
VERY HIGH TEMPERATURE
CHALCOGENIDES
DISPERSIONS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
HAFNIUM COMPOUNDS
MIXTURES
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RARE EARTH COMPOUNDS
REFRACTORY METAL COMPOUNDS
SAMARIUM COMPOUNDS
SOLUTIONS
TRANSITION ELEMENT COMPOUNDS
YTTERBIUM COMPOUNDS
YTTRIUM COMPOUNDS
ZIRCONIUM COMPOUNDS
360202* - Ceramics
Cermets
& Refractories- Structure & Phase Studies
360204 - Ceramics
Cermets
& Refractories- Physical Properties