Effect of Sr/Mg co-doping on the structural, dielectric, and electrical properties of CaCu3Ti4O12 ceramics

Thanks to their exceptional dielectric constant, the CaCu3Ti4O12 (CCTO) ceramic materials have significantly sparked a lot of research in capacitor applications. Nevertheless, large dielectric loss and a relatively low breakdown voltage preclude their practical applications. The current work focuses on improving the capacitor–varistor properties by simultaneously adding Sr and Mg to the lattice of calcium copper titanate Ca1-xSrxCu2.9Mg0.1Ti4O12 (with x = 0, 0.1, 0.15, and 0.2). A correlation between the grain boundary and the dielectric/electrical properties of CCTO was systematically established. It is apparent that the combination of Sr and Mg doping ions gives rise to an obvious enhancement of the dielectric and nonlinear properties of CCTO ceramic. Besides, the increase in Sr content brings about the formation of secondary phases (TiO2, CuO, and SrTiO3) at grain boundaries detected by EDS and Raman measurements. More importantly, the dielectric constant increased with increasing Sr content while retaining excellent frequency stability [102–106 Hz]. Among ceramic samples, the Ca0.9Sr0.1Cu2.9Mg0.1Ti4O12 sample shows the lowest dielectric loss (− 0.05 at 1 kHz), as well as the highest nonlinear coefficient (α = 10) and breakdown voltage (− 1009 V/cm). Additionally, the grain boundary effect played an important role in the dielectric and electric responses. The improvement of dielectric losses and nonlinear behaviors is attributed to this enhancement of grain boundary resistance.