Microstructures and Dielectric Properties of Cu-deficient and Excess CaCu3Ti4O(12) Polycrystalline Ceramics

다국어 초록 (Multilingual Abstract)

We report the important roles of Cu composition in CaCu3Ti4O(12) (CCTO) polycrystalline ceramics. These roles include influencing the microstructural change and remarkably high dielectric constant, ε(r) in a relatively low frequency region. For this purpose, CaCu(2.8)Ti4O(12) (Cu2.8) and CaCu(2.9)Ti4O(12) (Cu2.9) powders with a Cu-deficient composition, CaCu(3.1)Ti4O(12)(Cu3.l) and CaCu(3.2)Ti4O(12) (Cu3.2) powders with a Cu-excess composition and CaCu3Ti4O(12) (Cu3.0) (CCTO) powder were prepared. All of these samples were calcined at 950℃ for 24h, and then sintered at 1060℃ for 12h using a conventional solid-state ceramic process. As the Cu composition decreased, the Cu-deficient samples changed from a duplex microstructure including abnormally grown grains and fine grains to a microstructure almost fully covered with fine grains without any abnormally grown grains. However, the Cu-excess samples showed fine-grained microstructures in which no abnormally grown grains were observed with Cu-rich seco1ldary phases segregated at the grain boundaries compared with CCTO. Relative dielectric constants of the, ε(r) values of the samples were strongly affected by the size and population of abnormally grown grains which were varied with the amount of Cu-rich secondary phases.