Microstructure and electrical properties of sol-gel derived Ni-doped CaCu3Ti4O12 ceramics

Dielectric properties and varistor performance of sol-gel prepared Ni-doped calcium copper titanate ceramics (CaCu3NixTi4O12+x, x=0, 0.1, 0.2, 0.3) were investigated. SEM and XRD were used in the microstructural studies of the specimens and the electrical properties were investigated for varistors. XRD patterns show that the CCTO ceramics were single phase with no Cu-rich phase. SEM results indicated that the samples had smaller grain sizes than those synthesized by traditional solid-state reaction methods. The experimental results show that the highest dielectric constant and lower dielectric loss occur when x=0.2. When x=0.3, the lowest leakage current is obtained and the maximum value reaches 0.295; meanwhile, the lowest threshold voltage and nonlinear coefficient are found, the minimum values of them are 1326 V/mm and 3.1, respectively.