Stefan G. Ebbinghaus

Nonintrinsic origin of the colossal dielectric constants in Ca Cu 3 Ti 4 O 12

The dielectric properties of

Colossal dielectric constants in single-crystalline and ceramic CaCu3Ti4O12 investigated by broadband dielectric spectroscopy

\mathrm{Ca}{\mathrm{Cu}}_{3}{\mathrm{Ti}}_{4}{\mathrm{O}}_{12}

Broadband dielectric spectroscopy on single-crystalline and ceramic CaCu3Ti4O12

, a material showing colossal values of the dielectric constant, were investigated over a broad temperature and frequency range extending up to

Broadband dielectric response of Ca Cu 3 Ti 4 O 12 : From dc to the electronic transition regime

1.3\phantom{\rule{0.3em}{0ex}}\mathrm{GHz}

Powder neutron diffraction of SrNbO2N at room temperature and 1.5 K

. A detailed equivalent-circuit analysis of the results and two crucial experiments, employing different types of contacts and varying the sample thickness were performed. The results provide clear evidence that the apparently high values of the dielectric constant in

Orbital Ordering and Spin-Ladder Formation in La2RuO5

\mathrm{Ca}{\mathrm{Cu}}_{3}{\mathrm{Ti}}_{4}{\mathrm{O}}_{12}

High- and low-temperature La2RuO5 by powder neutron diffraction

are nonintrinsic and due to electrode polarization effects. The intrinsic properties of

Phase formation and phase transition of Ln1–xCaxCoO3–δ (Ln= La, Er) applied for bifunctional air electrodes

\mathrm{Ca}{\mathrm{Cu}}_{3}{\mathrm{Ti}}_{4}{\mathrm{O}}_{12}

Crystal structure and optical properties of the new 8O polytype of Ca2Ta2O7

are characterized by charge transport via hopping of localized charge carriers and a relatively high dielectric constant of the order of 100.

Two Ti-doped distrontium ruthenium tetraoxides: Sr2Ru0.93Ti0.07O4 and Sr2Ru0.81Ti0.19O4.

In the present work, the authors report results of broadband dielectric spectroscopy on various samples of CaCu3Ti4O12 (CCTO), also including single-crystalline material, which so far was only rarely investigated. The measurements extend up to 1.3 GHz, covering more than nine frequency decades. We address the question of the origin of the colossal dielectric constants and of the relaxational behavior in this material, including the second relaxation reported in several recent works. For this purpose, the dependence of the temperature- and frequency-dependent dielectric properties on different tempering and surface treatments of the samples and on ac-field amplitude is investigated. Broadband spectra of a single crystal are analyzed by an equivalent circuit description by assuming two highly resistive layers in series to the bulk. Good fits could be achieved, including the second relaxation, which also shows up in single crystals. The temperature- and frequency-dependent intrinsic conductivity of CCTO is consistent with the variable range hopping model. The second relaxation is sensitive to surface treatment and, in contrast to the main relaxation, is also strongly affected by the applied ac voltage. Concerning the origin of the two insulating layers, we discuss a completely surface-related mechanism by assuming the formation of a metal-insulator diode and a combination of surface and internal barriers.In the present work, the authors report results of broadband dielectric spectroscopy on various samples of CaCu3Ti4O12 (CCTO), also including single-crystalline material, which so far was only rarely investigated. The measurements extend up to 1.3 GHz, covering more than nine frequency decades. We address the question of the origin of the colossal dielectric constants and of the relaxational behavior in this material, including the second relaxation reported in several recent works. For this purpose, the dependence of the temperature- and frequency-dependent dielectric properties on different tempering and surface treatments of the samples and on ac-field amplitude is investigated. Broadband spectra of a single crystal are analyzed by an equivalent circuit description by assuming two highly resistive layers in series to the bulk. Good fits could be achieved, including the second relaxation, which also shows up in single crystals. The temperature- and frequency-dependent intrinsic conductivity of CCTO is c...