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Title:Donor doping of K0.5Na0.5NbO3 ceramics with strontium and its implications to grain size, phase composition and crystal structure
Authors:Hreščak, Jitka (Author)
Dražić, Goran (Author)
Deluca, Marco (Author)
Arčon, Iztok (Author)
Kodre, Alojz (Author)
Dapiaggi, M. (Author)
Rojac, Tadej (Author)
Malič, Barbara (Author)
Benčan, Andreja (Author)
Files:.pdf Manuscript_text.pdf (2,11 MB)
 
Language:English
Work type:Not categorized (r6)
Tipology:1.01 - Original Scientific Article
Organization:UNG - University of Nova Gorica
Abstract:In this study, the particular effects of A-site donor doping in a lead-free piezoceramic material K0.5Na0.5NbO3 (KNN) doped with Sr2+, i.e., the crystal-structure change, the secondary-phase formation and the grain-size decrease, were investigated. The already-reported causes of these effects upon doping KNN were critically discussed and a mechanism of the effects’ formation was suggested and experimentally supported with advanced analytical methods. Extended X-ray absorption fine structure (EXAFS) analyses proved that the Sr occupies the perovskite A-sublattice, and locally modifies the KNN monoclinic structure to cubic. With the help of Sr K-edge EXAFS and wavelength-dispersive X-ray spectroscopy, the Sr was found to be homogenously distributed in the KNN perovskite lattice with 0.5, 1 and 2% Sr and no Sr segregation on the nano level was found in any of the studied samples with transmission electron microscopy. 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.
Keywords:perovskite, potassium sodium niobate, donor doping, cation vacancies
Year of publishing:2017
Number of pages:10
Numbering:37
COBISS_ID:4638715 Link is opened in a new window
URN:URN:SI:UNG:REP:K6AF7WGV
DOI:10.1016/j.jeurceramsoc.2016.12.053 Link is opened in a new window
License:CC BY-NC-ND 4.0
This work is available under this license: Creative Commons Attribution Non-Commercial No Derivatives 4.0 International
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Record is a part of a journal

Title:Journal of the European Ceramic Society
Publisher:Elsevier
ISSN:0955-2219
Year of publishing:2017

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