Potassium-Sodium Niobate (KNN) Powder Synthesis for Lead-Free Piezoelectric Ceramics
HRÍBALOVÁ S. 1, NECINA V. 1, ŠIMONOVÁ P. 1, KOTRBOVÁ L. 1, BALDISSERRI C. 2, CAPIANI C. 2, MERCADELLI E. 2
1 University of Chemistry and Technology, Prague, Prague, Czechia; 2 National Research Council of Italy, Institute of Science, Technology and Sustainability for Ceramics, (CNR-ISSMC, former ISTEC), Faenza, Italy
Lead-free piezoelectric ceramics are attracting increasing research interest due to the challenge to develop promising lead-free materials able to replace lead-containing systems. Potassium sodium niobate, KxNax-1NbO3 (KNN) is one of the lead-free alternatives, however, the relationships between processing, microstructure and properties of undoped KNN are not that well documented in the literature. Moreover, as the preparation contains a large number of steps, usually including laboratory KNN powder synthesis, the reproducibility of results can be remarkably challenging [1].
The goal of the present contribution is therefore to shed some light on (i) the reproducibility and influence of precursors for the powder synthesis and choice of commercial powders for KNN ceramics preparation; (ii) the influence of processing parameters such as sintering temperature, dwell time and heating rate on conventionally sintered KNN ceramics; (iii) relationships between microstructure and properties (dielectric, piezoelectric, thermal, and mechanical) of KNN ceramics. Different sintering methods (spark plasma sintering / SPS and hot-pressing / HP) will be briefly discussed as well.
This work confirms that slight deviations in the solid-state synthesis of KNN powders affect the results of fundamental studies on sintering and microstructure-property relations [2]. The quality of different powder batches or commercial powders plays a crucial role in the characteristics and performance of the final KNN ceramics.
References:
[1] R. Beltrami, E. Mercadelli, C. Baldisserri, C. Galassi, F. Braghin, N. Lecis: Synthesis of KNN powders: Scaling effect of the milling step. Powder Technology, 375, 101-108, 2020. doi: 10.1016/j.powtec.2020.07.098.
[2] S. H?íbalová, V. Ne?ina, P. Šimonová, W. Pabst, C. Capiani, C. Baldisserri, E, Mercadelli: Potassium-sodium niobate (KNN) powder synthesis - Influence of precursors and comparison with commercial KNN powders (in preparation).
Acknowledgement:
This work was supported from the OP RDE project IGRA@UCTP, registration no.: CZ.02.2.69/0.0/0.0/19_073/0016928“, funded by the ESF.
S.H. acknowledges support from JECS Trust that allowed S.H. to perform significant part of this work at CNR-ISSMC, Faenza, Italy.