Investigation of sintering kinetics of (KxNa1-x)NbO3 based lead-free piezoceramics produced by Spark Plasma Sintering

Reference Presenter Authors
(Institution)
Abstract
08-130 Camila Alves Souza Souza, C.A.(Universidade Federal de São Paulo); Lente, M.H.(Universidade Federal de São Paulo); Eiras, J.A.(Universidade Federal de São Carlos); The search for piezoelectric compositions to replace Lead Titanium Zirconate (PZT) increases the investigations of new lead-free piezoelectric compositions due to the environmental hazards generated by the Pb element. The system (Kx, Na1-x)NbO3 (KNN) is considered one of the most promising candidates for this purpose, due to its promising piezoelectric and dielectric properties. However, this material still presents some ceramic processing challenges. Rather, it is difficulty to produce KNN ceramics with densities close to the ideal one and with a homogeneous microstructure, reflecting in poor dielectric and piezoelectric properties. In this way, new sintering routes become a great ally to achieve the desired microstructure and. In this work, it was conducted both the study of the densification of lead-free piezoelectric ceramics based on (Kx, Na1-x)NbO3 via Spark Plasma Sintering and the study of the sintering kinetics through the determination of the Master Sintering Curve (MSC) of the undoped KNN. In addition, the effect of either the CuO doping on KNN sintering kinetics or the effect of a lower pressure applied during the sintering process were analyzed in a complementary manner. Thus, three batch of samples were prepared. In one, undoped KNN ceramics were sintered at different heating rates applying the maximum allowable pressure. In a second one, a low uniaxial pressure was applied during the sintering. Subsequently, in a third batch, Cu-doped KNN samples (hardener element) were produced. The results obtained were correlated with microstructural, structural and electrical properties. In parallel, the dilatometry data from the SPS equipment were used for the construction of the MSC and to obtain the apparent activation energy of the undoped KNN ceramics. The obtained activation energy of the KNN produced by SPS was compared to the those from the conventional sintering route and possible densification mechanisms present in the SPS process were proposed.
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