ISSN:
1573-4803
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract The nature of blackening of 8 mol % Sc2O3-ZrO2, caused by imposing high current densities on this material at 800° C and P O, 〈 10−7 atm, has been investigated by transmission electron microscopy. The material studied was in the form of hot pressed polycrystalline discs with equiaxed grains 2 to 4 μm in size with a cubic fluorite structure. There is also evidence of small coherent precipitates of tetragonal phase embedded within the matrix of the cubic fluorite phase. The current-blackened samples contained numerous polycrystalline aggregates, with crystallites 10 to 20 nm in size, and they were usually found at the grain boundaries. The lattice parameter of this phase is virtually identical to that of the original cubic-fluorite matrix phase. The electron diffraction pattern showed, however, weak reflections forbidden by the fcc symmetry of the parent phase. These reflections can only be indexed as primitive cubic, and it is proposed that grain boundary phase consists partly of non-stoichiometric zirconium suboxides (ZrO2−x). The analysis of energy dispersive X-ray spectrum and electron diffraction patterns of the polycrystalline phase shows no evidence of the presence of metallic zirconium, as has been postulated previously.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00541827
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