Temperature-independent dc conduction in $BaTiO3$-based ceramic capacitors

In this work, measurements of temperature-dependent dc conduction current in $BaTiO3$-based multilayer ceramic capacitors have been made. It was found that there is tunnel-like conduction current near Curie temperature of $BaTiO3$ where the current showed a temperature-independent characteristic. For the study of this abnormal phenomenon, the structural nature of insulating solids of practical importance is emphasized. A new concept has been introduced to explain the positive temperature coefficient anomaly in $BaTiO3$-based ceramic dielectrics. It was presumed that a Schottky process dominates the conduction current at the Curie temperature. It was also assumed that the Schottky process is controlled by the phase transition of $BaTiO3$-based ceramics near the Curie temperature where the effective work function, which changes with the temperature, is inherently related to the density of the paraelectric cubic crystals. Based on the proposed model, it was found that the calculated results are accurately correlated with the experimental ones.