Polymeric citrate precursor route to the synthesis of the high dielectric constant oxide, CaCu3Ti4O12

Using citric acid and ethylene glycol, a polymeric precursor of the above compound was obtained at low temperatures (13 5 degreesC) which on subsequent heat treatments led to pure CaCu3Ti4O12 at 1000 degreesC On sintering further at 1000 degreesC (20 h), the disks show high density (98%) and the dielectric constant was of the order of 3000 at I kHz. The dielectric loss varies between 0.3 and 0.35 (till 100 kHz) beyond that it increases sharply from 0.35 to 0.7 in the frequency range of 100-500 kHz. Our studies on dielectric properties of the above oxide, synthesized by the ceramic method and sintered under the same conditions, led to a dielectric constant of around 2200 at 1 kHz. The dielectric constant decreases with frequency in the oxides obtained by either of the above methods. Scanning electron micrographs (SEM) show much larger grains (nearly spherical) of 2-4 mum in the solid obtained by the ceramic route while the grains were much smaller (0.5 - 1.0 mum) in the oxide prepared by the polymeric citrate precursor route. (C) 2002 Elsevier Science B.V. All rights reserved.