Spark plasma texturing: A strategy to enhance the electro-mechanical properties of lead-free potassium sodium niobate ceramics


Controlling the sintering and microstructure of lead-free potassium sodium niobate ((K1-xNax)NbO3, KNN) ceramics is of primary importance to optimize its piezoelectric / ferroelectric properties. However, sintering dense and monophasic KNN remains a challenge. Here, we prepare KNN ceramics using spark plasma texturing (SPT), a modified spark plasma sintering (SPS) technique, in which uniaxial pressure is applied in an edge-free configuration, allowing ceramics to deform in the radial direction. Densification at low temperatures (1000 degrees C) and for short times (20 min) is achieved by SPT accompanied by constrained grain growth (average grain size =1.4 mu m), resulting in enhanced piezoelectric properties (d(33) =108 pC N-1 and g(33) = 21.2 x 10(-3) Vm N-1). In addition, and of relevance, SPT KNN ceramics reveal a more homogeneous electrical microstructure postulated to be related with a reduced diffusion and local segregation of defects, resulting in grain cores and shells with more similar capacitances and conductivities. Our work brings new practical understanding to sintering of KNN and demonstrates the potential of alternative densification strategies for improved lead-free dielectrics. (C) 2020 Elsevier Ltd. All rights reserved.



subject category

Materials Science


Pinho, R; Tkach, A; Zlotnik, S; Costa, ME; Noudem, J; Reaney, IM; Vilarinho, PM

our authors


This work was developed within the scope of the project CICECO-Aveiro Institute of Materials (UIDB/50011/2020 & UIDP/50011/2020), financed by national funds through the FCT/MCTES and when appropriate co -financed by FEDER under the PT2020 Partnership Agreement. The authors acknowledge the critical analysis of the impedance spectroscopy data and constructive input of Professor Derek Sinclair (University of Sheffield). Rui Pinho acknowledges FCT for financial support, under the scholarship SFRH/BD/120969/2016. Ian M. Reaney acknowledges the support of Engineering and Physical Sciences Council research grant, EP/L017563/1.

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