Colossal dielectric permittivity and electrical properties of the grain boundary of Ca1−3x/2YbxCu3−yMgyTi4O12 (x=0.05, y=0.05 and 0.30)

Dielectric properties of Ca1−3x/2YbxCu3−yMgyTi4O12 (x=0.05, y=0.05 and 0.30) prepared using a modified sol-gel method and sintered at 1070 °C for 4 h were investigated. The mean grain sizes of the CaCu3Ti4O12 and co-doped Ca0.925Yb0.05Cu3−yMgyTi4O12 (y=0.05 and 0.30) ceramics were ≈15.86, ≈3.37, and ≈2.32 μm, respectively. Interestingly, the dielectric properties can be effectively improved by co-doping with Yb3+ and Mg2+ ions to simultaneously control the microstructure and properties of grain boundaries, respectively. These properties were improved over those of single-doped and un-doped CaCu3Ti4O12 ceramics. A highly frequency−independent colossal dielectric permittivity (≈104) in the range of 102-106 Hz with very low loss tangent values of 0.018-0.028 at 1 kHz were successfully achieved in the co-doped Ca0.925Yb0.05Cu3−yMgyTi4O12 ceramics. Furthermore, the temperature stability of the colossal dielectric response of Ca1−3x/2YbxCu3−yMgyTi4O12 was also improved to values of less than ±15% in the temperature range from −70 to 100 °C.