Dielectric and Nonohmic Properties of CaCu3Ti4O12/SrTiO3 Ceramics

In this work, (1 − x)CaCu3Ti4O12-xSrTiO3 [(1 − x)CCTO/xST, x = 0% to 2%] ceramic samples were prepared by the solid-state reaction method. The dielectric and electrical properties of CaCu3Ti4O12 (CCTO) and CaCu3Ti4O12/SrTiO3 (CCTO/ST) ceramics were investigated. The results show that a small amount of Sr2+ can enter the lattice of CCTO. The mean grain size of the ceramic samples increased greatly for x = 0.5% and then decreased for x = 0.75% to 2%. ST addition and Sr2+ preferential occupancy in CCTO grains should be responsible for the change of the microstructure. Interestingly, the dielectric constant (ε) of the 0.5% ST-added sample increased significantly while the dielectric loss (tan δ) remained low. With further increase of the ST content, the ε and tan δ values of the CCTO ceramics decreased monotonically while the nonlinear current–voltage properties were significantly enhanced. The change in the potential barrier height is thought to be the main cause for the opposite behaviors in the dielectric properties and nonohmic characteristics.