Papers by Keyword: CaCu3Ti4O12 Ceramics

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Authors: Vito Raineri, Patrick Fiorenza, Raffaella Lo Nigro, Derek C. Sinclair
Abstract: Scanning probe microscopy with conductive tips has been used to image the dielectric properties of ceramics with giant permittivity. In particular, measurements in impedance mode and of local resistivity allowed to image the permittivity map on polycrystalline materials. Such imaging allows to correlate the dielectric properties with the local sample structure and with defects inside the single grains of the polycrystalline ceramics. However, artifacts due to surface imperfections should be distinguished from bulk properties and eliminated.
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Authors: Qiu Xiang Liu, Xin Gui Tang, Yan Ping Jiang, F. L. Dong
Abstract: Two kinds ceramics of pure CaCu3Ti4O12 (CCTO) and Sr/Mg doped (Ca0.25Cu0.75)0.5Sr0.5TiO3 + xMgO (x=0.01, 0.03, 0.05, 0.1, denoted as CCST-M-1, CCST-M-3, CCST-M-5, CCST-M-10, respectively) were prepared using the traditional solid phase reaction method. The dielectric properties were measured by HP 4194A Impedance/Gain-Phase Analyzer with the frequency range from 100 Hz to 1MHz. The temperature dependence of dielectric constant and loss tangent were measured for different frequencies. The variation relation of the critical temperature with the frequency was fitted theoretically which is in agreement with the Arrhenius law for pure CCTO. According to a variable power law to describe the paraelectric dielectric constant of ferroelectrics with diffuse phase transitions, the theoretical fitting was carried out for doped samples, and it was suggested that all doped samples exhibited the Debye-like relaxation. Among the doped and pure CCTO samples, CCST-M-1 was of the lowest dielectric loss at the whole measurement frequency, and whose I–V response curve was nonlinear suggesting a non-ohmic contact. The complex-impedance analysis results showed that the reduction in dielectric loss of CCST-M-1 sample can be attributed to the increase of grain boundary resistance. It is expect that these results are helpful to promote the CCTO-related materials to practical applications.
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