Influence of point defects on grain boundary diffusion in oxides. Final technical report, July 1, 1990--June 30, 1993
Grain boundary diffusion coefficients of {sup 57}Co and {sup 59}Co in polycrys. NiO, NiO bicrystal, and polycrys. Fe{sub 3}O{sub 4} were determined at various oxygen pressures at 750 C. For NiO, the low oxygen pressure region (<10{sup {minus}10} MPa) displayed constant grain boundary diffusion coefficients as the oxygen pressure decreased, indicating an extrinsic region in which the impurity-induced defects dominated the intrinsic defects. At greater oxygen pressures, the intrinsic defects (Ni vacancies) dominated the extrinsic defects, causing the diffusion to increase with pressure. For Fe{sub 3}O{sub 4}, at low oxygen pressures (<10{sup {minus}16} MPa), the grain boundary diffusion coefficient increased when the pressure decreased, owing to interstitial type diffusion; at >10{sup {minus}15} MPa, the diffusion increased with pressure, owing to vacancy type diffusion. D{sub gb} of Co ions in Fe{sub 3}O{sub 4} is proportional to pO{sub 2}{sup {minus}2/3} in the low pressure region and to pO{sub 2}{sup 2/3} in the high pressure region, indicating similar mechanisms in the grain boundary diffusion and volume diffusion. Ratio of D{sub gb}/D was about 10{sup 3}.
- Research Organization:
- Pennsylvania State Univ., University Park, PA (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- FG02-90ER45414
- OSTI ID:
- 10194695
- Report Number(s):
- DOE/ER/45414-3; ON: DE94003164; BR: KC0201030
- Resource Relation:
- Other Information: PBD: [1993]
- Country of Publication:
- United States
- Language:
- English
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