Giant dielectric constant response of the composites in ternary system CuO–TiO2–CaO

The subsolidus phase relations of the ternary system CuO–TiO2–CaO sintered at 950 °C in air have been determined by powder X-ray diffraction method. Only one ternary compound CaCu3Ti4O12 was found in this system. From room-temperature dielectric property mapping at 10 kHz, a giant dielectric constant (εr>104) was observed for most of the ceramic composites in the CuO-rich region and in the region along the CaO–CuO binary line. The composites in the CaCu3Ti4O12-rich region were found to give a comparable giant dielectric constant when sintered at 1050 °C. The particular microstructure of larger grains with predominant phase surrounded by smaller grains with the secondary phases was found in such composites with a high dielectric constant. The relations between structures and dielectric properties were investigated. An internal barrier layer capacitance effect is the most probable mechanism to explain this particular dielectric behavior.