Microstructure and enhanced dielectric response in Mg doped CaCu3Ti4O12 ceramics

•ε′ of a CaCu2.95Mg0.05Ti4O12 ceramic remains above 25 k while f ≤ 200 kHz.•Tanδ can be below 0.05 from 20 Hz to 30 kHz for a CaCu2.9Mg0.1Ti4O12 ceramic.•Very low tanδ ∼0.017 can be observed in a CaCu2.9Mg0.1Ti4O12 ceramic.•Fluctuation of ε′ was less than ±10% in a CCMTO ceramic from 20 to 240 °C.

CaCu3−xMgxTi4O12 (CCMTO, x = 0, 0.05, 0.1 and 0.2) ceramics were prepared by the sol–gel method. Effects of Mg-doping on the giant dielectric response in CaCu3Ti4O12 (CCTO) ceramics were investigated and discussed. A significantly enhanced giant dielectric response was obtained in CCMTO ceramics, but the dielectric constant (ε′) step decreased with increasing Mg-doping content. High ε′ ∼2.52 × 104 and low loss tangent (tanδ) ∼0.017 at room temperature and 1 kHz were successfully accomplished in the CaCu2.9Mg0.1Ti4O12 ceramic sintered at 1080 °C for 8 h. The fluctuation of ε′ of the above sample was less than ±10% in the temperature range of 20–240 °C at 100 kHz. And the characteristic frequency shifts to higher frequency with the increasing measuring temperature. The present results indicate that Mg doping can bring about apparent change in both microstructures and dielectric properties for CCTO.