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    Item type:Publication, Access status: with files ,
    What do we know about surface charges on cracks in ferroelectric ceramics?
    (2010)
    Engert, Andrea Raphaela
    ;
    Felten, Frank
    ;
    Jelitto, Hans
    ;
    Schneider, Gerold A.
    The present work investigates the static and time dependent electric potential distribution around cracks in a poled ferroelectric ceramic by Kelvin Probe Force Microscopy (KFM). In a first step a Vickers indentation crack in poled lead zirconate titanate (PZT) was subjected to static electric fields of up to 500 V/mm in poling direction, and the potential distribution around the crack as measured. In a second step, the polarity of the applied voltage was reversed against the poling direction during the measurement of the potential. Using a simple model, an effective dielectric constant of the crack, as well as the surface charge density on the crack face were calculated as a function of the distance from the crack tip, the applied field and the time. The results are discussed with reference to free charges on the crack surface, electrically induced domain switching at the crack tip and crack bridging.
    Publicationtype: Conference Paper
      620  844
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    Item type:Publication, Access status: with files ,
    Experimenteller Aufbau zur Messung der Energiefreisetzungsrate für Risswachstum in PZT unter elektromechanischer Last
    (2005)
    Jelitto, Hans
    ;
    Felten, Frank
    ;
    Schneider, Gerold A.
    Four-point-bending V-notched specimens of PZT poled parallel to the long axis are fractured under conditions of controlled crack growth in a custom-made device. In addition to the mechanical loading an electric field is applied parallel or anti parallel to the poling direction. This is a typical loading condition for the application of piezo- and ferroelectric ceramics, respectively. To determine the different contributions to the total energy release rate the mechanical and piezoelectric compliance as well as the electrical capacitance of the sample are acquired continuously with a special technique as a function of the crack length. The derivation of the data with respect to the crack surface allows calculating all parts of the total energy release rate on the basis of a single bending experiment for the first time. The main focus here is the presentation of the experimental method.
    Publicationtype: Conference Paper
      812  527