Influence of Fabrication Parameters on the Phase Formation and Dielectric Properties of CaCu_3Ti_4O_(12 )Ceramics  

作　　者：Qian Zheng Huiqing Fan 

机构地区：[1]State Key Laboratory of Solidification Processing,School of Materials Science and Engineering,Northwestern Polytech-nical University,Xi'an 710072,China

出　　处：《Journal of Materials Science & Technology》2012年第10期920-926,共7页材料科学技术（英文版）

基　　金：financially supported by the National Natural Science Foundation of China (No. 51172187);the SRPDF (No. 20116102130002);the 111 Program of MOE(No. B08040);the Xi an Science and Technology Foundation of China (Nos. CX1261-2, CX1261-3 and XA-AM-201003)

摘　　要：The giant dielectric permittivity materials CaCu3Ti4012 （CCTO） were synthesized by conventional solid-state reaction techniques. X-ray diffraction and Raman scattering for the powder indicate that the powder calcined at 950 ℃ for 12 h has been completely transformed into the purer CCTO phase. Furthermore, the morphology and size of the grains of the ceramics sintered at 1090 ℃ in the dwell time range from 0 to 26 h were observed by scanning electron microscopy （SEM）. Dielectric properties of the polycrystalline CCTO ceramics were characterized in a broad frequency range （100 Hz-1 MHz） and at a temperature ranged from 300 to 500 K. The longer sintering time may lead to more defect structures and the enhanced conductivity, also leads to substantial improvements in permittivity. Grain size and density differences were not large enough to account for the enhancement in dielectric permittivity. Based on the observations, it is believed that the primary factor affecting dielectric behavior is the development of internal defects. The CCTO ceramics sintered at 1090 ℃ for 15 h exhibit lower dielectric loss （-0.05） near room temperature, and the dielectric relaxation behavior above 1 kHz was observed to follow the Arrhenius law. The activation energy （Ea） of 0.65 eV indicates that the doubly ionized oxygen vacancies in the grain boundaries are responsible for the dielectric relaxation of the CCTO ceramics.The giant dielectric permittivity materials CaCu3Ti4012 （CCTO） were synthesized by conventional solid-state reaction techniques. X-ray diffraction and Raman scattering for the powder indicate that the powder calcined at 950 ℃ for 12 h has been completely transformed into the purer CCTO phase. Furthermore, the morphology and size of the grains of the ceramics sintered at 1090 ℃ in the dwell time range from 0 to 26 h were observed by scanning electron microscopy （SEM）. Dielectric properties of the polycrystalline CCTO ceramics were characterized in a broad frequency range （100 Hz-1 MHz） and at a temperature ranged from 300 to 500 K. The longer sintering time may lead to more defect structures and the enhanced conductivity, also leads to substantial improvements in permittivity. Grain size and density differences were not large enough to account for the enhancement in dielectric permittivity. Based on the observations, it is believed that the primary factor affecting dielectric behavior is the development of internal defects. The CCTO ceramics sintered at 1090 ℃ for 15 h exhibit lower dielectric loss （-0.05） near room temperature, and the dielectric relaxation behavior above 1 kHz was observed to follow the Arrhenius law. The activation energy （Ea） of 0.65 eV indicates that the doubly ionized oxygen vacancies in the grain boundaries are responsible for the dielectric relaxation of the CCTO ceramics.

关 键 词：Microstructure Dielectric properties Impedance spectroscopy RELAXATION 

分 类 号：TQ174.758[化学工程—陶瓷工业] X16[化学工程—硅酸盐工业]