Defect clusters and superstructures of Zr{sup 4+} dissolved Ni{sub 1{minus}x}O
- National Sun Yat-sen Univ., Kaohsiung (Taiwan, Province of China). Inst. of Materials Science and Engineering
Ni{sub 1{minus}x}O (x < 0.001) powders, pure and mixed with pure ZrO{sub 2} or yttria-partially stabilized zirconia (Y-PSZ), were sintered and then annealed at 1,573 and 1,873 K for up to 300 h to investigate the dopant dependence of defect clustering in the Ni{sub 1{minus}x}O lattice. Transmission electron microscopic observations coupled with energy X-ray analysis indicated that the dissolution of Zr{sup 4+} (ca. 2.0 mol% with or without co-dopant Y{sup 3+} < 0.3 mol%) but not Ni{sup 3+} caused defect clustering, which was more rapid at 1,873 than 1,573 K and which preferred to nucleate at interfaces and dislocations. The paracrystalline distribution of defects was found to be nearly 3.5 and 2.5 times the lattice parameter of Ni{sub 1{minus}x}O for Zr-doped and (Zr,Y)-codoped Ni{sub 1{minus}x}O, respectively. The predominantly dissolved Zr{sup 4+} cations, in octahedral sites with charge- and volume-compensating nickel and oxygen vacancies (i.e., Zr{sup oct}{open_square}{sub n}O{sub 6{minus}m}{open_square}{sub m}), could create local domains in which Ni{sup 3+} should be expelled and, thus, in the vicinity the paracrystalline state and then the spinel Ni{sub 3}O{sub 4} could precipitate in local domains. The spinelloid, a superstructure of spinel with a relatively high Zr{sup 4+} content (ca. 3.5 mol%), appeared only for the Ni{sub 1{minus}x}O particles located at Y-PSZ grain boundaries.
- OSTI ID:
- 305381
- Journal Information:
- Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 2 Vol. 140; ISSN 0022-4596; ISSN JSSCBI
- Country of Publication:
- United States
- Language:
- English
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