Mechanochemical synthesis and giant dielectric properties of CaCu 3 Ti 4 O 12

CaCu 3 Ti 4 O 12 powder has been synthesized by mechanochemical milling (C-m) and solid-state reaction (C-ssr) techniques. C-m powder has a grain size of ~24 nm as determined from X-ray diffraction and FE-SEM measurements. The grain size of C-m ceramics has increased to 20 μm compared to a size of 3 μm for C-ssr ceramics after sintering at 1,050 °C for 10 h. Giant dielectric constant was observed in both ceramics with that of C-m larger than that of C-ssr. Impedance results show that the grain conductivity of C-m is more than two orders of magnitude lower than that of C-ssr, whereas its grain boundary conductivity is larger than that of C-ssr. These results are supported by the EDX results that show Cu-enriched grain boundaries in C-m ceramics.