Local electromechanical properties of ferroelectric materials for piezoelectric applications
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Local electromechanical properties of ferroelectric materials for piezoelectric applications A. L. Kholkin, I. K. Bdikin, V. V. Shvartsman, Department of Ceramics and Glass Engineering and Center for Research in Ceramic and Composite Materials (CICECO), University of Aveiro, 3810-193 Aveiro, Portugal A. Orlova, D. Kiselev, A. A. Bogomolov Department of Physics, Tver State University, 170000 Tver, Russia S.-H. Kim INOSTEK Inc., Ansan, Gyeonggi 425-791, Korea
ABSTRACT Local electromechanical characterization is becoming prerequisite for the development of ferroelectric-based piezoelectric devices including multilayer actuators, micromotors, piezoelectric filters and, especially, microelectromechanical systems (MEMS), which combine piezoelectric elements and control electronics on the same chip. In this work, we present the results of local electromechanical characterization of several important ferroelectric materials including Pb(Zr,Ti)O3 (PZT) and (Pb,La)(Zr,Ti)O3 (PLZT) in both thin film and ceramic form. Local piezoelectric hysteresis measurements are performed by the piezoelectric force microscopy (PFM) that detects small electric field-induced deformation on the nanoscale, e. g., within the single grain of a polycrystalline material. A number of novel phenomena is observed with increasing dc bias voltage including the jump of ferroelectric domain wall to the grain boundary, the “fingerlike” instability of domain wall, and the local phase transition into ferroelectric phase.
INTRODUCTION Lead-based ferroelectric materials including Pb(Zr,Ti)O3 (PZT) and (Pb,La)(Zr,Ti)O3 (PLZT) remain the main candidates for the miniaturization of piezoelectric devices because of their large electromechanical strain (e.g., PZT near the morphotropic phase boundary) and the absence of electromechanical hysteresis (e.g., PLZT with high La content). These properties will be inevitably changed on a nanoscale due to the confinement and grain size effects, influence of interfaces, domain wall pinning and creep, etc. Therefore, the local characterization of piezoelectric materials is becoming of increasing importance in materials science of ferroelectrics. In this work, we studied the local electromechanical properties of PZT of several compositions and PLZT 9.75/65/35 ceramics. In recent years, the study of the local properties of piezoelectrics has been frequently performed by using a new technique called piezoelectric force microscopy (PFM) [1]. The advantages of PFM as compared to other piezoelectric techniques (e.g., laser interferometry or resonance method) include extremely high spatial resolution (down to a few nanometers) and high sensitivity to local deformation, which makes this method well suitable for studying the local properties of ferroelectrics, including those with weak piezoelectric effect. The disadvantages are due to the extremely inhomogeneous electric field and mechanical stress distributions that make the quantification of the local piezoelectric effect extremely difficult, if not impossible. Also, the re
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