Donor doping of K0.5Na0.5NbO3 ceramics with strontium and its implications to grain size,phase composition and crystal structure |
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| Affiliation: | 1. Electronic Ceramics Department, Jozef Stefan Institute, Ljubljana, Slovenia;2. Jozef Stefan International Postgraduate School, Ljubljana, Slovenia;3. Laboratory for Materials Chemistry, National Institute of Chemistry, Ljubljana, Slovenia;4. Materials Center Leoben Forschung GmbH, Leoben, Austria;5. Institut für Struktur- und Funktionskeramik, Montanuniversitaet Leoben, Leoben, Austria;6. Department of Low and Medium Energy Physics, Jožef Stefan Institute, Ljubljana, Slovenia;7. Laboratory of Quantum Optics, University of Nova Gorica, Nova Gorica, Slovenia;8. Faculty of Mathematics and Physics, University of Ljubljana, Ljubljana, Slovenia;9. Department of Earth Sciences “Ardito Desio”, University of Milan, Milano, Italy;1. Departament de Química Inorgànica, Universitat de Barcelona, 08028 Barcelona, Spain;2. Department of Applied Physics, Universitat Politècnica de Catalunya, 08034 Barcelona, Spain;3. Laboratory of SPMS, Ecole Centrale Paris, Grande voie des vignes, 92295 Chatenay-Malabry Cedex, France;1. School of Energy, Power and Mechanical Engineering, North China Electric Power University, Beijing 102206, PR China;2. Department of Materials Science and Engineering, Advanced Materials Processing and Analysis Center, University of Central Florida, Orlando, FL 32816, USA;1. Key Laboratory of Transparent Opto-Functional Advanced Inorganic Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 588 Heshuo Road, Shanghai 201899, PR China;2. University of Chinese Academy of Sciences, Beijing 100049, PR China;1. Université François Rabelais de Tours, CNRS, CEA, ENIVL, GREMAN UMR 7347, IUT de BLOIS 15 rue de la chocolaterie, CS 2903, 41029 Blois Cedex, France;2. Laboratoire des Sciences des Procédés et des Matériaux, CNRS, LSPM – UPR 3407, Université Paris 13, Sorbonne Paris Cité, 99 Avenue J.B. Clément, 93430 Villetaneuse, France;3. Université de Montpellier 2, IES, UMR 5214, Place E. Bataillon, 34095 Montpellier, France;1. State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, PR China;2. Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu 610209, PR China;3. Department of Materials Science, Sichuan University, Chengdu, 610064, PR China |
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| 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. |
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| Keywords: | Perovskite Potassium sodium niobate Donor doping Cation vacancies |
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