Influence of Nb5+ions on the dielectric properties of CaCu3Ti4O12 ceramics

In this work, Nb5+ doped CCTO ceramic with high dielectric constant (epsilon r) and a very low dielectric loss (tans) is reported. Powder XRD analysis confirmed the cubic perovskite structure and the Rietveld profile shows the goodness of fit below 2. The XPS analysis confirmed the presence of Ca 2p, La 3d, Cu 2p, Ti 2p, O 1 s, and C 1 s, all of which exhibited their expected oxidation states. The SEM micrographs revealed a grain size of 1.01 +/- 0.07 mu m for pure and 1.77 +/- 0.13 mu m for Nb5+doped CCTO. The Nb5+doped CCTO exhibited high epsilon r approximate to 1.26 x 105 at 50 Hz with low tans approximate to 0.85 at 1 kHz for 673 K in comparison with pure CCTO. The Nyquist plots established a deviation from Debye type relaxation with a negative temperature coefficient of resistance (NTCR) type behaviour.