Dresden 2009 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 5: High-k and low-k Dielectrics

DF 5.1: Vortrag

Montag, 23. März 2009, 15:00–15:20, WIL B321

Dielectric properties of A_2/3Cu₃Ti₄O₁₂ (A = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy) — •Jürgen Sebald¹, Stephan Krohns¹, Peter Lunkenheimer¹, Stefan Riegg², Stefan G. Ebbinghaus³, and Alois Loidl¹ — ¹Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany — ²Solid State Chemistry, University of Augsburg, 86135 Augsburg, Germany — ³Institute for Chemistry, Martin-Luther University Halle-Wittenberg, 06120 Halle, Germany

New materials showing the phenomenon of a very high dielectric constant (є′ > 10³), similar to the famous CaCu₃Ti₄O₁₂ (CCTO), are in the focus of scientific interest. Materials with extremely high ("colossal") dielectric constants (CDC) are urgently needed for future electronics. Today it is more or less commonly accepted that the CDC is due to extrinsic effects like "internal barrier layer capacitors" (IBLC) or "surface barrier layer capacitors" (SBLC). Polarisation effects at grain boundaries or other internal barriers can generate nonintrinsic colossal values of є′ (IBLC). In addition, SBLCs, arising, e.g., from a formation of Schottky diodes at the contact-bulk interfaces, can generate a contribution to the colossal value of є′ as has been shown for CaCu₃Ti₄O₁₂. To investigate these models and to search for alternatives for CCTO, frequency- and temperature-dependent dielectric measurements on differently treated samples of various CCTO related materials were performed. To check for possible correlations of magnetic structure and dielectric properties, magnetic-field dependent dielectric spectroscopy was carried out.