A novel (1 − x)CaCu3Ti4O12 − xY2/3Cu3Ti4O12 composite ceramic was developed. Two perovskite-like grains, i.e.
CaCu3Ti4O12 grains of 1–2 μm and Y2/3Cu3Ti4O12 grains of 4–6 μm, can be both detected in the samples. High
Schottcky barrier height and grain boundary resistance were formed via combining these two perovskite-like
phases, which plays the critical role on the varistor and dielectric performance. Greatly enhanced nonlinear
coefficient of 9.88 and very low dielectric loss of 0.02 can be achieved in the composite ceramics accompanied
with the permittivity of ~2000, compared with reported results of 2–6 and 0.05–0.8 for general CaCu3Ti4O12
ceramics. This varistor–capacitor multifunctional characteristic makes it a promising material in the field of
over voltage protections of electronic devices.