Comparison of colossal permittivity of CaCu3Ti4O12 with commercial grain boundary barrier layer capacitor

The properties of a commercial grain boundary barrier layer (GBBL) SrTiO3-based capacitor are analyzed in terms of capacitance C and resistivity R of two RC elements, one for grains and one for grain boundaries. Results are compared with those of CaCu3Ti4O12 (CCTO) samples showing giant permittivity, measured in the same conditions and analyzed with the same method. All CCTO samples investigated here show higher permittivity than GBBL. This is shown to be related to a higher capacitance of the grain boundaries. However, the electric losses of CCTO measured via conventional tan(δ) are found significantly higher. They are related to a resistivity of the grain boundaries lower than in GBBL capacitor. A better control of the grain boundaries in CCTO possibly via a core-shell synthesis described here, followed by thermal post treatments under a controlled atmosphere as it is performed for GBBL capacitors, is suggested to improve the resistance of CCTO dielectrics.