期刊
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
卷 29, 期 3, 页码 419-424出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.jeurceramsoc.2008.06.019
关键词
Oxygen deficiency; Defects; Electron microscopy; Dielectric properties; TiO(2)
资金
- Engineering and Physical Sciences Research Council [EP/F012403/1, EP/F035853/1, EP/F067828/1] Funding Source: researchfish
- EPSRC [EP/F012403/1, EP/F067828/1, EP/F035853/1] Funding Source: UKRI
Undoped TiO(2) exhibited deterioration in microwave (MW) dielectric loss as it reached its maximum density due to the reduction of Ti(4+) to Ti(3+) causing oxygen vacancies at high sintering temperatures. By adding small amounts of acceptor dopants with ionic radii between 0.5 and 0.95 angstrom, reduction during sintering was suppressed. The upper limit of ionic radius was discrete with almost no observed effect using dopants > 0.96 angstrom ionic radius. In addition, the microwave dielectric loss of undoped TiO(2) could be improved by annealing at 1500 degrees C for 10 h in air, presumably as a result of re-oxidation. High loss samples exhibited a dark 'core' to the naked eye which was absent in low loss ceramics. Transmission electron microscopy revealed that grains in the dark core contained planar defects attributed to the condensation of O vacancies onto specific crystallographic planes, in a manner similar to that observed in Magnelli phases. (c) 2008 Elsevier Ltd. All rights reserved.
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