In this research, the dielectric and non-Ohmic properties of nano/micro-sized CaTiO3/CaCu3Ti4O12 composites (NCTO/MCCTO) with different weight percent of CTO (0, 7, 15, and 30 wt%) were examined as a new engineering design. NCTO was prepared after high energy ball milling of calcined CaCO3 and TiO2 mixture. Micro-sized CCTO was synthesized after calcination of CaCO3, CuO, and TiO2 mixture at 1000 °C. According to the TEM, BET, and SEM analyses; the mean particle size of NCTO and MCCTO was 80 nm and 2.5 μm, respectively. The NCTO/MCCTO powder composites were prepared from direct mixing of pre-synthesized NCTO and MCCTO. After the sintering of green body composites at 1100 °C for 5 h, both relative density and grain size of NCTO/MCCTO composites decreased with the increase in NCTO content. It was found that the abnormal grain growth in the sintered MCCTO changed to the normal grain growth in NCTO/MCCTO composites. The best dielectric properties (ϵr: 7050, tanδ: 0.02) was observed for NCTO/MCCTO with 15 wt% CTO. This unique dielectric constant was ascribed to the large grain size of CCTO, and the reduced dead zone of CTO with a low dielectric constant. Due to uniform distribution of CTO with the small size of 0.3–1.5 μm at grain boundaries of CCTO with a large grain size of 5 μm, the number of active interfaces were increased sharply and consequently the maximum breakdown electric field of 7 kV/cm and the nonlinear coefficient of 15 were obtained for NCTO/MCCTO with 15 wt% of NCTO. Therefore, the MCCTO-NCTO composite with 15 wt% of NCTO is a promising candidate for the capacitor and energy storage applications.
