Significantly enhanced dielectric constant and breakdown strength in crystalline@amorphous core-shell structured SrTiO3 nanocomposite thick films

A sol-gel based coating technology was utilized to improve the dielectric properties of SrTiO3 (STO) thick films based on crystalline@amorphous core-shell nanostructure. In this route, poly(vinyl pyrrolidone) (PVP) was used as the surface modification agent to optimize the dispersibility of nanoparticles, which played an important role in promoting the dielectric homogeneity in the nanocomposite films. The crystalline@amorphous structure could achieve both the enhanced dielectric constant and high breakdown strength because the external amorphous STO matrix shells were capable of undertaking higher applied field while the internal STO nano-crystalline cores supplied more polarization charges. Compared with the amorphous matrix, the dielectric constant of the modified film could be increased from 15 to 46 under the precondition of maintaining the high breakdown strength (170 MV/m). Consequently, the calculated energy density is 5.9 J/cm3. Furthermore, based on the electric field simulation result, it can be concluded that interface blocking effect created by the amorphous layers and reduced electric field intensification by PVP modification led to the enhancement in breakdown strength.