Raman spectroscopy for the investigation of indentation-induced domain texturing in lead zirconate titanate piezoceramics Marco Deluca, a,b, * Rau ´ l Bermejo, a Hannes Gru ¨ nbichler, a,b Volker Presser, c Robert Danzer a,b and Klaus G. Nickel d a Institut fu ¨ r Struktur- und Funktionskeramik, Montanuniversita ¨ t Leoben, Peter Tunner Straße 5, 8700 Leoben, Austria b Materials Center Leoben Forschung GmbH, Roseggerstraße 12, 8700 Leoben, Austria c A. J. Drexel Nanotechnology Institute, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, USA d Institute for Geoscience, Eberhard Karls Universita ¨t Tu ¨ bingen, Wilhelmstraße 56, 72074 Tu ¨ bingen, Germany Received 22 February 2010; accepted 26 April 2010 Available online 29 April 2010 The study of the close relationship between crack propagation and domain switching is of extreme importance in the reliability of PbZr 1x Ti x O 3 (PZT) devices. We performed domain imaging in the neighbourhood of indentation cracks on poled and non-poled PZT bulk specimens using polarized micro-Raman spectroscopy. Non-destructive Raman measurements helped to correlate the indentation-induced domain texture with the crack growth resistance on both samples. Hence, polarized micro-Raman spectroscopy offers the potential to locally investigate regions of interest in complex piezoelectric devices. Ó 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Keywords: Perovskites; PZT; Raman spectroscopy; Micro-indentation The outstanding electro-mechanical coupling of lead zirconate titanate (PbZr 1x Ti x O 3 , PZT) is due to its structural peculiarities in the neighbourhood of the mor- photropic phase boundary (MPB) [1–4]. These properties are exploited for the production of high-precision piezo- electric devices. One of the most common applications is constituted by PZT-based multilayer piezoelectric actua- tors (MPAs) used to control modern fuel injection sys- tems [5,6]. Reliability problems in MPAs are generally related to the fact that such structures are prone to crack- ing and delamination, both during initial poling of the pie- zoelectric material and during service [7,8]. It is known that the growth of cracks in piezoceram- ics such as PZT is strongly influenced by the ferroelastic effect. During crack propagation, ferroelectric domains tend to align with the direction of the tensile stress pres- ent at the crack tip. The domains will re-orient them- selves perpendicular to the crack propagation direction. This domain switching process consumes elas- tic energy, thus reducing the energy release rate for fur- ther crack propagation [9–14]. As a result, cracks parallel to the poling direction of a PZT are significantly shorter than cracks propagating perpendicularly (for the same applied load) [9–12]. Numerous attempts have been made to correlate crack growth resistance (CGR) in PZT with its poling state by means of notched speci- mens and micro-indentations in dependence of applied load and temperature [11–16]. The main difficulty in these studies has always been associated with the lack of a reliable method to locally investigate the poling state of very-small-grain piezoceramics such as PZT. For instance, surface sensitive techniques such as piezor- esponse force microscopy (PFM) [17] are generally suit- able for the investigation of ferroelastic switching in large-grain piezoceramics. Neutron diffraction [18,19] seems promising, but its rather broad lateral resolution hinders its application on micro-sized piezoceramic lay- ers. In this regard, polarized micro-Raman spectroscopy has been recently used for domain analysis and imaging in PZT polycrystals, directly or in the neighbourhood of Vickers indentations [20–24]. This technique has the advantage of being easy to use (compared to synchro- tron X-ray, for instance [25,26]) with high spatial resolu- tion and capability to penetrate the transparent PZT material for several tens of microns. In this work, we provide experimental analysis of domain orientation using Raman spectroscopy around 1359-6462/$ - see front matter Ó 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.scriptamat.2010.04.040 * Corresponding author. Tel.: +43 3842 402 4113; fax: +43 3842 402 4102; e-mail: marco.deluca@mcl.at Available online at www.sciencedirect.com Scripta Materialia 63 (2010) 343–346 www.elsevier.com/locate/scriptamat