Effect of the MgO substitution for CuO on the properties of CaCu_3Ti_4O_(12) ceramics

摘要

In this work, the effect of MgO substitution for CuO on the dielectric properties of CaCu_3Ti_4O_(12) (CCTO) was studied. Ceramic samples of CaCu_(3-x)Mg_xTi_4O_(12) were prepared by a two-step solid-state reaction. The samples were sintered at 600 °C for 2 h and then heated to the final sintering temperature of 1100 °C for 8 h. The lattice parameter of CCTO decreases with Mg substitution from X-ray diffraction (XRD) analysis, since the ionic radius of Mg～(2+) is smaller than that of Cu～(2+). 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 x 10~5 at/= 100 Hz 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.