Co-doping effects of A-site Y~(3+) and B-site Al~(3+) on the microstructures and dielectric properties of CaCu_3Ti_4O_(12) ceramics

摘要

Different doping elements have been used to reduce the dielectric losses of CaCu_3Ti_4O_(12) ceramics, but their dielectric constants usually are undesirably decreased. This work intends to reduce their dielectric losses and simultaneously enhance their dielectric constants by co-doping Y~(3+) as a donor at A site and Al~(3+) as an acceptor at B site for substituting Ca~(2+) and Ti~(4+), respectively. Samples with different doping concentrations x = 0, 0.01, 0.02, 0.03, 0.05 and 0.07 have been prepared. It has been shown that their dielectric losses are generally reduced and their dielectric constants are simultaneously enhanced across the frequency range up to 1 MHz. The doped sample with x = 0.05 exhibits the highest dielectric constant, which is well over 104 for frequency up to 1 MHz and is about 20% higher than the undoped sample. Impedance spectra indicate that the doped samples have much higher grain boundary resistance than the undoped one.