Effect of the MgO substitution for CuO on the properties of CaCu3Ti4O12 ceramics

Abstract

In this work, the effect of MgO substitution for CuO on the dielectric properties of CaCu3Ti4O12 (CCTO) was studied. Ceramic samples of CaCu3−xMgxTi4O12 were prepared by a two-step solid-state reaction. The samples were sintered at 600°C for 2h and then heated to the final sintering temperature of 1100°C for 8h. The lattice parameter of CCTO decreases with Mg substitution from X-ray diffraction (XRD) analysis, since the ionic radius of Mg2+ is smaller than that of Cu2+. Mg substitution in CCTO causes apparent change in microstructure with much smaller grains due to the grain growth inhibition. The maximum of the dielectric constant can reach to 7.8×105 at f=100Hz for Mg substitution with x=0.6. The sample with Mg substitution (x>0.2) yields an apparent semicircle in the impedance spectra. The correlation between the microstructure and dielectric properties suggests the presence of a thin barrier layer forming at the grain boundary.