Piezoelectric nanoindentation
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W.C. Oliver MTS Corporation, Oak Ridge, Tennessee 37831
E. Karapetian Suffolk University, Boston, Massachusetts 02108
Sergei V. Kalininb) Condensed Material Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (Received 25 July 2005; accepted 8 December 2005)
Piezoelectric nanoindentation (PNI) has been developed to quantitatively address electromechanical coupling and pressure-induced dynamic phenomena in ferroelectric materials on the nanoscale. In PNI, an oscillating voltage is applied between the back side of the sample and the indenter tip, and the first harmonic of bias-induced surface displacement at the area of indenter contact is detected. PNI is implemented using a standard nanoindentation system equipped with a continuous stiffness measurement system. The piezoresponse of polycrystalline lead zirconate titanate (PZT) and BaTiO3 piezoceramics was studied during a standard nanoindentation experiment. For PZT, the response was found to be load independent, in agreement with theoretical predictions. In polycrystalline barium titanate, a load dependence of the piezoresponse was observed. The potential of piezoelectric nanoindentation for studies of phase transitions and local structure-property relations in piezoelectric materials is discussed.
In the last decade, nanoindentation has been established as a quantitative tool for the characterization of mechanical properties of materials on the nanoscale. The load dependence of the indenter displacement has been used for characterization of local elastic modulus,1 pressure induced phase transitions,2 fracture toughness,3 etc. The interpretation of nanoindentation experiments in terms of material properties is based on the method developed by Oliver and Pharr.1 However, recent progress in nanoelectromechanical systems, actuators, and ferroelectric-based devices exhibiting or utilizing piezoelectric or electrostrictive coupling has necessitated quantitative studies of not only mechanical but also electromechanical phenomena on the nanoscale. To date, the primary tool to study these phenomena has been piezoresponse force microscopy (PFM), which allows imaging of the local piezoelectric properties with sub-10 nm resolution.4–6 However, due to the extremely complex dynamic behavior of the cantilever based force detection
Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] DOI: 10.1557/JMR.2006.0081 552
J. Mater. Res., Vol. 21, No. 3, Mar 2006 http://journals.cambridge.org Downloaded: 13 Mar 2015
system, this technique is semiquantitative at best. In addition, the load applied to the sample is limited by the stiffness of the cantilever, and PFM generally cannot be used to measure load-induced phenomena in piezoelectric materials. Due to the low loads, PFM is also sensitive to surface contamination. Here, we demonstrate a quantitative approach to electromechanical measurements on the nanoscale based on nanoindentation with piezoelectric sample activation, further referred to as piezoelectric na
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