Improvement of the Nonlinear and Dielectric Properties of CaCu3Ti4O12 Ceramics by Nickel Doping

CaCu3Ti4O12 (CCTO) ceramics have been widely demonstrated due to their high dielectric constant and are considered potential materials for capacitor applications. However, its high dielectric loss (tan & delta;), which is greater than 0.1, makes it unsuitable for a lot of uses. Generally, CCTO doped with Ni ions exhibits low nonlinear properties and a high tan & delta;. In this work, CaCu2.9Ni0.1Ti4O12 (with x = 0/0.1/0.2) ceramics were synthesized by a semi-wet route. Significantly, the CaCu2.8Ni0.2Ti4O12 (Ni02) ceramic revealed an enhancement in breakdown electric voltage (E-b & AP; 4208 V/cm) and nonlinear coefficient (& alpha; & AP; 7.69) with a considerably decrease in dielectric loss (tan & delta; & AP; 0.017). The mean grain size for Ni02 ceramic decreased from 6.15 to 2.23 & mu;m. Density increased at first from 91.05 to 92.88% and then decreased by 89.6% with grain size reduction. The decrease in its mean grain size was attributed to the incorporation of Ni ions into Ti sites, as explained by DRX, EDS, and Raman results. The band gap energy increased from 2.25 eV for undoped CCTO ceramic to 3.54 eV for Ni02 ceramic. Additionally, all the ceramic samples present a high dielectric constant (& epsilon;) in the range of 10(4)-10(5). According to the complex impedance spectroscopy results, the electrically heterogeneous CCTO microstructure is responsible for the high dielectric response. Moreover, the enhancement of dielectric and electric properties is attributed to the grain boundary effect.