Improved dielectric,nonlinear and magnetic properties of cobalt-doped CaCu3Ti4O12 ceramics

The dielectric properties and voltage–current nonlinearity of the pure and various cobalt-doped CaCu₃Ti₄O₁₂ (Co-doped CCTO) prepared by solid-state reactions were investigated. The improved dielectric properties in the Co-doped CCTO, with a dielectric constant $\text{ε'}$ ≈7.4?×?10⁴ and dielectric loss $\text{tan}\text{δ}$?≈?0.034, were observed in the sample with a Co doping of 5% (CCTO05) at room temperature and 1?kHz. The related multi-relaxations, RII (?20 to 40?°C) and RIII (100–150?°C), were demonstrated to be a Debye-like relaxation and a Maxwell–Wagner relaxation related to oxygen vacancies. The low dielectric loss of CCTO05 was associated with the high grain boundary resistance and the increase in cation vacancies. The improved nonlinear electrical properties (CCTO05, with nonlinear coefficients $\text{α}$?≈?5.22 and breakdown electric field ${\text{E}}_{\text{b}}$?≈?300.46?V/cm) and the ferromagnetism in Co-doped CCTO were also discussed.