Decrease in the dielectric loss of CaCu3Ti4O12 at high frequency by Ru doping

CaCu3-xRuxTi4O12 (x=0, 0.03, 0.05 and 0.07) electronic ceramics were fabricated using a conventional solid-state reaction method. The microstructure, grain sizes and dielectric properties as well as the impedance behaviours of the ceramics were carefully investigated. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) results indicate that ruthenium (Ru) dopant inhibits the growth of grains during the sintering process by promoting the formation of high melting point oxides of Ca and Ti. The study on the frequency dependence of dielectric properties suggests that Ru doping shifts the dielectric loss peak of CCTO to a much lower frequency, thereby reducing the dielectric loss of CCTO at high frequency (f> 1.0 MHz) accordingly. When doped with proper amount of Ru, the high frequency dielectric loss of CCTO is reduced to a very low value (tan delta < 0.05). Our study conclusively suggests that Ru-doped CCTO, with sufficiently low dielectric loss and decent permittivity, presents potential applications at high frequency.