Enhanced non−Ohmic properties and giant dielectric response of (Sm+Zn) co−doped CaCu3Ti4O12 ceramics

Abstract The non−Ohmic and giant dielectric properties of CaCu 3 Ti 4 O 12 and Ca 0.925 Sm 0.05 Cu 3 -x Zn x Ti 4 O 12 ( x = 0.0−0.10) ceramics prepared by a modified sol−gel method were studied. Influences of (Sm+Zn) co−dopants on the crystalline structure and microstructure of CaCu 3 Ti 4 O 12 ceramics were investigated. The lattice parameter value was slightly enhanced, while the grain size was greatly reduced by inclusion of (Sm+Zn) co−dopants. Interestingly, the dielectric loss tangent in the frequency range of 10 2 −10 6 Hz was significantly reduced (tan δ ≈ 0.041 at 1 kHz), whereas the dielectric permittivity was still too large (> 10 3 ). Furthermore, their nonlinear electrical properties were significantly enhanced. The nonlinear coefficient and breakdown electric field increased with increasing co−dopant concentration. The conduction activation energies of the grain and grain boundaries slightly changed, while the grain boundary resistance was greatly increased corresponding to a reduction in the mean grain size. The variations in giant dielectric and nonlinear electrical properties can be well described by the internal barrier layer capacitor effect.