EFFECT OF DOPANTS AND PROCESSING ON THE MICROSTRUCTURE AND DIELECTRIC PROPERTIES OF CaCu3Ti4O12 (CCTO)

Research has been conducted on the giant dielectric constant oxide CCTO and it has shown that the dielectric material has a giant permittivity (as large as 80,000) that is stable over a range of temperatures and frequencies. However, the typical CCTO ceramic usually has a dielectric loss of 0.1 or higher which needs to be reduced if this dielectric oxide is going to be used commercially. This research has shown that slow cooling in oxygen and annealing at 1000 degrees C can improve the dielectric loss properties. Doping with PbO also improved loss properties and lead to a two-fold increase in breakdown voltage. Co-doping with hafnia and calcia followed by annealing avoided sacrificing permittivity for loss leading to a CaCu3Ti4O12 ceramic with a giant dielectric constant of 69,000 and a tan delta of 0.027.