Finlay D. Morrison

CaCu3Ti4O12: One-step internal barrier layer capacitor

There has been much recent interest in a so-called “giant-dielectric phenomenon” displayed by an unusual cubic perovskite-type material, CaCu3Ti4O12; however, the origin of the high permittivity has been unclear [M. A. Subramanian, L. Dong, N. Duan, B. A. Reisner, and A. W. Sleight, J. Solid State Chem. 151, 323 (2000); C. C. Homes, T. Vogt, S. M. Shapiro, S. Wakimoto, and A. P. Ramirez, Science 293, 673 (2001); A. P. Ramirez, M. A. Subramanian, M. Gardel, G. Blumberg, D. Li, T. Vogt, and S. M. Shapiro, Solid State Commun. 115, 217 (2000)]. Impedance spectroscopy on CaCu3Ti4O12 ceramics demonstrates that they are electrically heterogeneous and consist of semiconducting grains with insulating grain boundaries. The giant-dielectric phenomenon is therefore attributed to a grain boundary (internal) barrier layer capacitance (IBLC) instead of an intrinsic property associated with the crystal structure. This barrier layer electrical microstructure with effective permittivity values in excess of 10 000 can be fa...

Electrical and structural characteristics of lanthanum-doped barium titanate ceramics

Single phase La-doped BaTiO3 with the formula Ba1−xLaxTi1−x/4O3: 0⩽x⩽0.20 was prepared by solid state reaction of oxide mixtures at 1350 °C, 3 days, in O2. The tetragonal distortion in undoped BaTiO3 decreased with x and samples were cubic for x⩾0.05. Both the tetragonal/cubic and orthorhombic/tetragonal transition temperatures decreased with x, but at different rates, and appeared to coalesce at x∼0.08. The value of the permittivity maximum at the tetragonal/cubic phase transition in ceramic samples increased from ∼10 000 for x=0 at 130 °C to ∼25 000 for x=0.06 at ∼−9 °C. At larger x, the permittivity maximum broadened, showed “relaxor”-type frequency dependent permittivity characteristics and continued to move to lower temperatures. Samples fired in O2 were insulating and showed no signs of donor doping whereas air-fired samples were semiconducting, attributable to oxygen loss.

Ferroelectric-paraelectric transition in BiFeO3: crystal structure of the orthorhombic beta phase.

A detailed investigation using variable temperature powder neutron diffraction demonstrates that

Ferroelectric-Paraelectric Transition inBiFeO3: Crystal Structure of the OrthorhombicβPhase

{\mathrm{BiFeO}}_{3}

Charge Compensation Mechanisms in La-Doped BaTiO3

undergoes a phase transition from the ferroelectric

Doping mechanisms and electrical properties of La-doped BaTiO3 ceramics

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Impedance spectroscopy of epitaxial multiferroic thin films

phase (rhombohedral,

Fatigue studies in compensated bulk lead zirconate titanate.

R3c

Impedance spectroscopy studies on polycrystalline BiFeO3 thin films on Pt/Si substrates

) to a paraelectric

Dielectric properties of spark-plasma-sintered BaTiO3

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