Effects of rare earth ionic doping on microstructures and electrical properties of CaCu3Ti4O12 ceramics

• The mean grain sizes decrease monotonically with reduced RE doping ionic radius.
• Doping gives rise to the monotonic decrease of ϵr with reduced RE ionic radius.
• The nonlinear coefficient and breakdown field increase with RE ionic doping.
• α of all the samples is associated with the potential barrier width rather than Φb.

Ca1–xRxCu3Ti4O12(R = La, Nd, Eu, Gd, Er; x = 0 and 0.005) ceramics were prepared by the conventional solid-state method. The influences of rare earth (RE) ion doping on the microstructure, dielectric and electrical properties of CaCu3Ti4O12 (CCTO) ceramics were investigated systematically. Single-phase formation is confirmed by XRD analyses. The mean grain size decreases monotonically with reduced RE ion radius. The EDS results reveal that RE ionic doping reduces Cu-rich phase segregation at the grain boundaries (GBs). Doping gives rise to the monotonic decrease of dielectric constant with reduced RE ionic radius but significantly improves stability with frequency. The lower dielectric loss of doped samples is obtained due to the increase of GB resistance. In addition, the nonlinear coefficient and breakdown field increase with RE ionic doping. Both the fine grains and the enhancement of potential barrier at GBs are responsible for the improvement of the nonlinear current–voltage properties in doped CCTO samples.

The dielectric constant decreases monotonically with reduced RE doping ion radius and is more frequency independent compared with that of pure CCTO sample.Figure optionsDownload as PowerPoint slide