Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5440524 | Journal of the European Ceramic Society | 2017 | 10 Pages |
Abstract
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.
Related Topics
Physical Sciences and Engineering
Materials Science
Ceramics and Composites
Authors
Jitka HreÅ¡Äak, Goran DražiÄ, Marco Deluca, Iztok ArÄon, Alojz Kodre, Monica Dapiaggi, Tadej Rojac, Barbara MaliÄ, Andreja Bencan,