Investigation on effects of CuO secondary phase on dielectric properties of CaCu3Ti4O12 ceramics

Two CaCu3Ti4O12 (CCTO) ceramics are separately sintered for 10 h at 975 and 1000 °C. The correlation between the microstructures and dielectric properties of the ceramics has been explored in this paper. The CuO secondary phase is separated out and locates at grain boundaries of the surface layer when the sintering temperature is raised up to 1000 °C. The presence of the CuO phase highly reduces the grain-boundary thickness and helps the grain growth, which together result in the increase of the dielectric constant. The low-frequency dielectric loss decreases due to the density improvement of the CCTO ceramics, and the high-frequency dielectric loss increases due to the reduction of the grain-boundary volume. The dielectric loss as low as 0.074 is obtained from the ceramic pellet sintered at 1000 °C.

► The CuO secondary phase is separated out when the sintering temperature is 1000 °C.
► The CuO phase is present at grain boundaries of the surface layer.
► The CuO phase highly reduces the thickness of grain boundaries and helps the grain growth.
► The dielectric loss as low as 0.074 is obtained from the pellet sintered at 1000 °C.
► The high-frequency dielectric loss increases due to the reduction of the grain-boundary volume.