Ni nanocrystals tuning low-frequency colossal permittivity of epitaxial BaTiO3 matrix

The ceramic-metal composites (CMCs) with colossal permittivity have great potential to be widely applied into embedded capacitors. However, the colossal permittivity of these composites could not be explained in the low-frequency region (<100 Hz) due to the uncontrollable grains and grain boundaries in the polycrystalline ceramic matrix. In this work, Ni nanocrystals (NCs) were embedded in epitaxial BaTiO3 films. According to modulate the interfacial stress, the epitaxial growth of BaTiO3 was not disturbed by the NCs, avoiding the influence of grains and grain boundaries in polycrystalline oxides matrix. By tuning the spacing of NCs, the controllable distribution of grain (Ni NCs) and grain boundary (contact interface between the Ni and BaTiO3) was realized. The effects of grain and grain boundary on the low-frequency colossal dielectric response of CMCs were revealed. This study provides an ideal CMCs model for designing and application of new thin-layer capacitors.