Role of co-doping (Sm3+ and Nb5+) and sintering conditions on the dielectric properties of CaCu3Ti4O12 ceramics

This research delves into the impact of Sm3+ and Nb5+ co-doping and the effect of sintering temperature on the grain size and the dielectric properties of CaCu3Ti4O12 (CCTO) ceramics synthesised via the sol-gel process. The Rietveld refinement provided detailed structural parameters, including atomic positions, bond lengths, bond angles, and R-factors, with a goodness of fit below 2 % with no secondary phases. The expected core levels for Ca 2p, Sm 3d, Cu 2p, Ti 2p, Nb 3d, and O 1s were verified by XPS analysis, suggesting that these materials were present in their expected oxidation states. As the sintering temperature is increased, the average grain size grew from 0.61 f 0.08 mu m to 2.38 f 0.32 mu m. Notably, the sample sintered at 1050 degrees C exhibited huge dielectric permittivity (epsilon' ti 105) with good stability in the wide frequency range (102-105 Hz) with significantly low dielectric loss. The complex impedance analysis was studied to separate the contributions of grain and grain boundary resistances while the Nyquist plot revealed that the Rgb ranged from 4.26 x 103 to 4.95 x 106 Omega. The AC conductivities of all the ceramics displayed semiconducting characteristics, exhibiting a frequency dependence that conforms to Jonscher's power law. The observed performance of the dielectric of the ceramic can be ascribed to the Internal Barrier Layer Capacitance (IBLC) model.