期刊
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
卷 37, 期 5, 页码 2073-2082出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.jeurceramsoc.2016.12.053
关键词
Perovskite; Potassium sodium niobate; Donor doping; Cation vacancies
资金
- Slovenian Research Agency [P2-0105, P1-0112, PR-03727]
- European Synchrotron Radiation Facility (ESRF), Grenoble, France [MA2315, LS-2275]
In this study, the particular effects of A-site donor doping, such as crystal-structure change, the secondary phase formation and the grain-size decrease, in a lead-free piezoceramic material K0.5Na0.5NbO3 (KNN) doped with Sr2+, were investigated. Extended X-ray absorption fine structure (EXAFS) analyses proved that Sr occupies the perovskite A-sublattice, and locally modifies the KNN monoclinic structure to cubic. Introducing Sr into the A-sublattice, as well as accounting for the charge-compensating A-site vacancies in the starting composition, causes increasing lattice disorder and microstrain, as determined from a Rietveld refinement of the synchrotron X-ray diffraction data. Above 2% Sr the system segregates the A-site vacancies in a secondary phase in order to release the chemical pressure, as revealed by Raman spectroscopy. All these effects result in an increasing number of low-angle grain boundaries that limit the grain growth and finally lead to a significant grain-size decrease. (C) 2017 Elsevier Ltd. All rights reserved.
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