Microstructure Evolution and Dielectric Characteristics of CaCu3Ti4O12 Ceramics with Sn-Substitution

The doping effect of Sn on the microstructure evolution and dielectric properties was studied in CaCu3Ti4-xSnxO12 polycrystals. Samples were produced by a conventional solid-state reaction method. Sintering was carried out at 1115 degrees C for 2-16 h in air. The dielectric constant and loss were examined at room temperature over a frequency range between 10(2) and 10(6) Hz. The microstructure was found to evolve into three stages. Addition of SnO2 led to an increase in density and advanced formation of abnormal grains. The formation of coarse grains with a reduced thickness of the boundary brought about an enhanced dielectric constant and a lower dielectric loss below similar to 1 kHz. EDS data showed the Cu-rich phase along the grain boundary, which should contribute to the improved dielectric constant according to the internal barrier layer capacitor model. After all, SnO2 was an effective dopant to elevate the dielectric characteristics of CaCu3Ti4-xSnxO12 polycrystals as a promoter for abnormal grain growth.