Very high thermal stability with excellent dielectric, and non-ohmics properties of Mg-doped CaCu3Ti4.2O12 ceramics

In this work, the nominal CaCu3-xMgxTi4.2O12 (0.00, 0.05 and 0.10) ceramics were prepared by sintering pellets of their precursor powders obtained by a polymer pyrolysis solution method at 1100 A degrees C for different sintering time of 8 and 12 h. Very low loss tangent (tan delta) < 0.009-0.014 and giant dielectric constant (epsilon') similar to 1.1 x 10(4)-1.8 x 10(4) with excellent temperature coefficient (Delta epsilon') less than +/- 15% in a temperature range of - 60 to 210 A degrees C were achieved. These excellent performances suggested a potent application of the ceramics for high temperature X8R and X9R capacitors. It was found that tan delta values decreased with increasing Mg2+ dopants due to the increase of grain boundary resistance (R (gb) ) caused by the very high density of grain, resulting from the substitution of small ionic radius Mg2+ dopants in the structure. In addition, CaCu3-xMgxTi4.2O12 ceramics displayed non-linear characteristics with the significant enhancements of a non-linear coefficient (alpha) and a breakdown field (E (b) ) due to Mg(2+)doping. The high values of epsilon' (14012), alpha (13.64) and E (b) (5977.02 V/cm) with very low tan delta value (0.009) were obtained in a CaCu2.90Mg0.10Ti4.2O12 ceramic sintered at 1100 A degrees C for 8 h.