Ferroelectric domains in coarse-grained lead zirconate titanate ceramics characterized by scanning force microscopy
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M.J. Hoffmann Institute of Ceramics in Mechanical Engineering, University of Karlsruhe, D-76131 Karlsruhe, Germany
G.A. Schneider Advanced Ceramics Group, Technical University Hamburg-Harburg, D-21073 Hamburg, Germany (Received 5 March 2003; accepted 1 May 2003)
Ferroelectric domain configurations in silver- and lanthanum-doped lead zirconate titanate (PZT) ceramics were characterized by scanning force microscopy using contact as well as piezoelectric response force [i.e., piezoelectric force microscopy (PFM)] modes. Coarse crystallites of hard and soft PZT ceramics (12 m in Ag-PZT and 30 m in La-PZT average grain size, respectively) with surface oriented in the {001} planes were chosen to characterize the domain configuration. Results show the conventional right-angled domain structures, which correspond to the {110} twin-related 90° and 180° domains of homogeneous width from 50 to 150 nm. The ability of PFM to image the orientation of pure in-plane arrays of domains (containing 90°-aa- and 180°-aa-types of domain boundaries) is highlighted, and a more detailed notation for in-plane domains is proposed. In addition to such periodical domain arrays, other ordered domains were found, having a misfit of 26° with respect to the {110} domain walls and the {100} surface. This array of domain walls could not be predicted with a geometrical analysis of the intersection of domain walls at the surface according to the conventional spatial array of {110} crystallographic planes. It could be explained only with {210} planes being the domain walls. The reason for this unconventional domain configuration is explained with the clamped conditions of the investigated crystallites in the polycrystalline material. I. INTRODUCTION
Direct observation of domain structures in typical bulk ferroelectric materials in the tetragonal variation at room temperature, such as barium titanate (BaTiO3),1–14 lead titanate (PbTiO3),13,15,16 and lead zirconate titanate Pb(Zrx,Ti1–x)O3 (PZT)9,17 has been extensively done in the last five decades. The reported multiple imaging methods, which are used to unambiguously characterize polarization arrangements during the direct observation of domains, are well established. Many of these investigations were based on optical microscopy (OM)1–6 and electron microscopic methods (scanning or transmission electron microscopy; SEM or TEM)6–11,15,17 to record either etch patterns, domain structures after spontaneous polarization arrangements, or electron diffraction patterns to identify the crystallographic relation of a domain or domain wall. To take advantage of the differential etch rate of ferroelectric domains,3 many of these studies were confined to crystallites with an [001] axis a)
Address all correspondence to this author. e-mail: [email protected] J. Mater. Res., Vol. 18, No. 8, Aug 2003
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normal to the specimen surface. These investigations have consistently confirmed the herringbone structures to be {110} crystallographic planes for 90° domain bo
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