Origin of significantly enhanced dielectric response and nonlinear electrical behavior in Ni2+-doped CaCu3Ti4O12: Influence of DC bias on electrical properties of grain boundary and associated giant dielectric properties

Abstract

CaCu3-xNixTi4O12 (x = 0, 0.05, and 0.10) powders were synthesized using a solid state reaction method. Phase structure and microstructure analyses revealed that all sintered CaCu3-xNixTi4O12 ceramics were of a pure phase. The CaCu3Ti4O12 ceramics had a dense microstructure and grain sizes were enlarged by doping with Ni2+. Interestingly, the dielectric permittivity was significantly enhanced, whereas the loss tangent was greatly suppressed to ∼0.046–0.034 at 1 kHz. All sintered ceramics exhibited non-Ohmic characteristics. Clarification of the influences of DC bias showed that the dielectric permittivity and loss tangent values were increased by DC bias. The resistance of grain boundaries and the associated conduction activation energy of CaCu3-xNixTi4O12 ceramics were reduced as the DC bias voltage increased. Therefore, the observed non-Ohmic behavior and significantly enhanced dielectric properties should be closely related to variation in the Schottky barriers at the grain boundaries.