Donor doping of K0.5Na0.5NbO3 ceramics with strontium and its implications to grain size, phase composition and crystal structure. Issue 5 (May 2017)

• Record Type: Journal Article
• Authors: Hreščak, Jitka; Dražić, Goran; Deluca, Marco; Arčon, Iztok; Kodre, Alojz; Dapiaggi, Monica; Rojac, Tadej; Malič, Barbara; Bencan, Andreja
• Is Part Of: Journal of the European Ceramic Society. Volume 37:Issue 5(2017)
• Page Start: 2073
• Page End: 2082
• Publication Date: 2017-05
• Subjects: Perovskite -- Potassium sodium niobate -- Donor doping -- Cation vacancies; Ceramic materials -- Periodicals; Composite materials -- Periodicals; Matériaux céramiques -- Périodiques; Composites -- Périodiques; Ceramic materials; Composite materials; Periodicals; Electronic journals; 666.05
• DOI: 10.1016/j.jeurceramsoc.2016.12.053
• Languages: English
• ISSNs: 0955-2219

Abstract

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 K0.5 Na0.5 NbO3 (KNN) doped with Sr 2+, 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.