Microstructural features and piezoelectric properties of spark plasma sintered lead-free K0.5Na0.5NbO3 ceramics

To replace lead containing (Pb, Zr) TiO 3 in piezoelectric devices, the (K, Na) NbO 3 system has shown great promise but has also encountered versatile properties, due to the volatilization of alkaline elements and difficulties in getting fully dense ceramics. K 0.5 Na 0.5 O 3 (KNN) powders are prep...

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Bibliographic Details
Published in:The European physical journal. ST, Special topics Special topics, 2022-12, Vol.231 (24), p.4185-4193
Main Authors: Monot-Laffez, Isabelle, Retoux, Richard, Zaghrioui, Mustapha, Bah, Micka, Dubernet, Marion, Dorvaux, Frédéric, Delorme, Fabian, Giovannelli, Fabien
Format: Article
Language:English
Subjects:
Annealing
Atomic
Ball milling
Ceramic powders
Ceramics
Classical and Continuum Physics
Condensed Matter Physics
Defects
Densification
Engineered Materials: Micro-Nano-Structure
Lead free
Materials Science
Measurement Science and Instrumentation
Molecular
Optical and Plasma Physics
Oxygen
Pellets
Physics
Physics and Astronomy
Piezoelectricity
Plasma sintering
Properties and Applications
Regular Article
Sintering (powder metallurgy)
Spark plasma sintering
Zirconium
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Summary:To replace lead containing (Pb, Zr) TiO 3 in piezoelectric devices, the (K, Na) NbO 3 system has shown great promise but has also encountered versatile properties, due to the volatilization of alkaline elements and difficulties in getting fully dense ceramics. K 0.5 Na 0.5 O 3 (KNN) powders are prepared by solid-state synthesis with a short-time planetary ball milling and shaped in a series of ceramic pellets using spark plasma sintering technique (SPS), resulting in highly dense ceramics. This sintering process operates in reducing conditions, and post-annealing in oxygen flow is required to recover a good electrical insulator material, to remove the residual strains in the ceramics and to eliminate possible carbon contamination from the graphite die. The structural and microstructural states of the ceramics, observed before and after post treatment, lead to the identification of the major defects encountered during SPS treatment. The resulting piezoelectric functional properties obtained on the series of pellets after oxygen annealing post treatment are measured. This study confirms that SPS technique is really successful in achieving very high and reproducible densification of KNN ceramics. After a post-annealing treatment, substantial piezoelectric properties improvement can be expected in such high densification and defect-free ceramics, suitable for integration in lead-free devices.
ISSN:1951-6355
1951-6401
DOI:10.1140/epjs/s11734-022-00573-y