Enhancement of dielectric and non-ohmic properties of graded Co doped CaCu3Ti4O12 thin films

The dielectric and nonlinear ohmic properties of pure CaCu3Ti4O12 and compositionally graded CaCu3-xCoxTi4O12 (x = 0, 0.05, 0.10, 0.15 and 0.20) thin films prepared by a modified sol-gel method were investigated. It is worth noting that the dielectric properties can be effectively improved via the gradient structure and Co2+ ions to control simultaneously the microstructure and growth rate of the grains, respectively. Interestingly, the low-frequency loss tangent (tan δ ≈ 0.016–0.017, 1 kHz) is greatly reduced and the high dielectric constant of ε’ ≈3143–3146 with good dielectric frequency stability is successfully achieved in the gradient CaCu3-xCoxTi4O12 film as compared to the un-doped CaCu3Ti4O12 film. In addition, the improved nonlinear ohmic properties of the gradient Co-doped CaCu3Ti4O12 thin films are discussed in detail. •The graded Co doped CCTO thin films are prepared by a dip coating method.•Enhanced dielectric frequency stability, e’≈3143-3146 and low tand ≈ 0.016-0.017 are achieved in Co-doped CCTO film.•The dielectric properties can be improved via the gradient structure and Co2+ ions.•The doping of gradient Co enhanced the nonlinear characteristics of CCTO films.