Dielectric Property of High Density CaCu_3Ti_4O_(12) Ceramics

High density CaCu3Ti4O12 ceramics was prepared by the hot-press sintering technique, and their microstructure, crystalline structure and dielectric property were investigated. The hot-pressed ceramics exhibit the microstructure of bimodal grain distribution with a high theoretical relative density of 98.3%. X-ray diffraction analysis shows that there is Cu2O minor phase in the hot-pressed ceramics whereas only CuO secondary phase exists after a further thermal treatment in ambience. Both the hot-pressed ceramics and its further thermally treated one exhibit two dielectric relaxations at room temperature, whereas the conventionally sintered ceramics have only one dielectric relaxation. Moreover, the hot-pressed CCTO ceramics have an extremely large low-frequency permittivity of 2×105, which further increases to nearly 1×106 through the ambient thermal treatment. The relation between microstructure and dielectric property is also discussed.