Regensburg 2007 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 3: Relaxor Ferroelectrics

DF 3.5: Vortrag

Montag, 26. März 2007, 16:10–16:30, H11

Defect structure in acceptor- and donor-doped PZT compounds — •Ruediger-A. Eichel — Edurad-Zintl-Institut, TU Darmstadt

The macroscopic properties of functional PZT compounds may considerably be modified by doping with rare-earth or transition-metal ions. High-frequency and multi-pulse EPR provides a local probe to characterize functional centers and defect states in acceptor- and donor-doped PZT ceramics.

In hard-doped Fe³⁺:PbTiO₃, high-frequency EPR prooved the existence of an iron-oxygen vacancy defect associate - the orientation of this defect dipole being oriented persistently along the crystallographic c-axis and anti-parallel with respect to the orientation of spontaneous polarization. For the other end-member composition Fe³⁺:PbZrO₃, again the creation of defect associates was observed. However, there is no persistent orientation of the corresponding defect dipole, but rather a ’multi-site* situation that is characterized in a way that the compensating oxygen vacancy may be localized at any of the six possible neighbour oxygen sites.

In contrast, acceptor-type Cu²⁺:PZT modifications show no association of the Cu²⁺ functional centers to charge-compensating oxygen vacancies. This conclusion is based on the observation of an orientation-independent, quasi-isotropic ²⁰⁷Pb-hyperfine coupling. As a consequence, considering the EPR results it could be predicted the Cu²⁺-modifications induce an ionic conductivity in PZT compounds.