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Role of doping and CuO segregation in improving the giant permittivity of CaCu3Ti4O12 |
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| Authors: | D Capsoni M Bini G Chiodelli CB Azzoni |
| Institution: | a Dipartimento di Chimica Fisica “M. Rolla” dell’Università, Università degli Studi di Pavia, viale Taramelli 16, IT 27100 Pavia, Italy b CNR-IENI, Sezione di Pavia, viale Taramelli 16, 27100 Pavia, Italy c INFM-Dipartimento di Fisica “A. Volta” dell’Università, via Bassi 6, 27100 Pavia, Italy |
| Abstract: | The dopant role on the electric and dielectric properties of the perovskite-type CaCu3Ti4O12 (CCTO) compound is evidenced. Impedance spectroscopy measurements show that the relevant permittivity value attributed to sintered CCTO is due to grain boundary (g.b.) effects. The g.b. permittivity value of the pure CCTO can be increased of 1-2 orders of magnitude by cation substitution on Ti site and/or segregation of CuO phase, while the bulk permittivity keeps values 90<εr<180. Bulk and g.b. conductivity contributions are discussed: electrons are responsible for the charge transport and a mean bulk activation energy of 0.07 eV is obtained at room temperature for all the examined samples. The g.b. activation energy ranges between 0.54 and 0.76 eV. Defect models related to the transport properties are proposed, supported by electron paramagnetic resonance measurements. |
| Keywords: | CaCu3Ti4O12 Cation doping EPR Defect models Impedance spectroscopy Conductivity measurements Grain boundary Giant permittivity Diffraction profile refinement |
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