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Ac Conductivity Relaxation Processes In Cacu₃Ti₄O₁₂ Ceramics: Grain Boundary And Domain Boundary Effects, Wei Li, Robert W. Schwartz
Ac Conductivity Relaxation Processes In Cacu₃Ti₄O₁₂ Ceramics: Grain Boundary And Domain Boundary Effects, Wei Li, Robert W. Schwartz
Materials Science and Engineering Faculty Research & Creative Works
The ac conductivity of CaCu₃Ti₄O₁₂ ceramics associated with electrical charge carrier motion (ions or vacancies) was investigated as a function of frequency at different temperatures. The long range migration of charge carriers within the ceramic is restricted by two kinds of insulating barriers, namely, grain boundaries and domain boundaries. The potential barriers associated with these boundaries lead to two anomalies in conductivity response and three frequency-dependent contributions to conductivity: long range diffusion of carriers, carrier migration localized within grains, and carrier migration localized within domains.
Maxwell-Wagner Relaxations And Their Contributions To The High Permittivity Of Calcium Copper Titanate Ceramics, Wei Li, Robert W. Schwartz
Maxwell-Wagner Relaxations And Their Contributions To The High Permittivity Of Calcium Copper Titanate Ceramics, Wei Li, Robert W. Schwartz
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Calcium copper titanate ceramics were fabricated by cold isostatic pressing at various calcination and sintering conditions. Depending on fabrication condition, three electrical responses were observed in the combined modulus and impedance plots, indicating the presence of two Maxwell-Wagner relaxations. These electrical responses show different response to temperature and applied field. The activation energies, as well as the driving force factors, were calculated for these relations. The determined activation energy values are in the range of 0.57 to 0.65 eV. The contribution of Maxwell-Wagner relaxations to the high permittivity of CCTO and related materials is briefly discussed.