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Sm2/3Cu3Ti4O12 ceramics with giant dielectric constant were successfully prepared by the traditional solid-state sintering process. The dielectric characteristics and relevant mechanism were systematically investigated. The dielectric constants of Sm2/3Cu3Ti4O12 ceramics can reach to 104 at 298 K and 1 kHz, and also exhibited two distinct thermal-activated dielectric relaxations in different temperature ranges. The dielectric relaxation at low temperatures was regarded as the effect of the polyvalence structures (Cu2+/Cu3+ and Ti3+/Ti4+) in grains due to the oxygen compensation during the sintering process, while the dielectric relaxation at high temperatures was induced by the grain boundary effects. The giant dielectric response in Sm2/3Cu3Ti4O12 ceramics can be associated with the heterogeneous structure and combined effect of the grain and grain boundary. [ABSTRACT FROM AUTHOR]

DyCuTiO ceramics were successfully synthesized by solid-state reaction process, and the crystal structure, microstructure and dielectric properties were systematically investigated. It has been found that DyCuTiO ceramics exhibit giant dielectric constants ( ε′ ~ 10 at 1 kHz and room temperature) and have two thermal-activated dielectric relaxations at low and high temperatures, which are quite similar to those reported in CaCuTiO ceramics. The low-temperature dielectric relaxation with the activation energy of 0.092 eV is supposed to be the intrinsic response originated from the defect structures of oxygen vacancy and aliovalences of Ti and Cu ions, which might make the grains semiconductive. Moreover, the heterogeneous structures especially the grain boundaries should be responsible for the high-temperature dielectric relaxation with the activation energy of 0.585 eV. The semiconducting grains and insulating grain boundaries thus play the key role as extrinsic origin for the giant dielectric response in DyCuTiO ceramics according to the internal barrier layer capacitor (IBLC) mechanism. [ABSTRACT FROM AUTHOR]