Effect of sintering temperature and Sm3+ doping on the dielectric properties and non-Ohmic behavior of Ca1-1.5xSmxCu3Ti4.2O12 (x = 0.05 and 0.10) ceramics

Abstract

The dielectric constant (ε’), dielectric loss tangent (tan δ), and non-Ohmic properties of Sm3+-doped CaCu3Ti4.2O12, i.e., Ca1-1.5xSmxCu3Ti4.2O12 (x = 0.05 and 0.10) ceramics sintered at 1080 °C and 1100 °C were studied. Interestingly, a giant- ε’ (∼9602–16169) with very low tan δ values (∼0.021–0.039) was attained in ceramics sintered at 1100 °C. Moreover, compared to undoped CaCu3Ti4.2O12 ceramics sintered at 1100 °C in our previous work, the tan δ values of Sm3+–doped CaCu3Ti4.2O12 ceramics (x = 0.05 and 0.10) sintered at 1100 °C were found to significantly decrease by 3.06% and 5.68%, respectively. Additionally, these ceramics exhibited non-Ohmic behavior with higher nonlinear coefficient (α)values of ∼ 8.7–22.1. It can be suggested that these very low tan δ values are associated with high grain boundary resistances (Rgb), as is confirmed by the impedance complex plane plot (Z* plot) for this material. Effects of Sm3+ doping and sintering temperature on CaCu3Ti4.2O12 ceramics played a significant role in increasing Rgb values as well as enhancing the nonlinear J-E relationship and dielectric properties of this material. FESEM and elemental mapping with EDXS spectra, as well as XRD techniques, were employed to elucidate the microstructural and structural nature of all ceramics. Moreover, XPS was performed to reveal the Cu+:Cu2+:Cu3+ ratios of these ceramics. The results indicated a semiconducting behavior of the grains. Additionally, it was found that the decreased ε’ values were correlated with lower Cu+:Cu2+ ratios and concurrently increasing levels of Sm3+ dopant.