Anomalous current-voltage behavior of $CaCu3Ti4O12$ ceramics

This letter reports on an investigation of dc current-voltage measured in $CaCu3Ti4O12$ ceramics. The experimental results show unusual $I-V$ behaviors associated with the electrically inhomogeneous nature of the grains (mixture of semiconducting and insulating regions) and dependence on delay time. The data strongly suggest that both the localization of current in the conductive region and local Joule self-heating effects are essential elements to explain the abrupt drop in the electric field. In addition, the hysteresis behavior recorded during the $I-V$ measurements shows strong dependence on delay time, i.e., the time needed for the polarization phenomena to occur.