Interfacial origin of enhanced energy density in SrTiO3-based nanocomposite films

SrTiO3-based films doped with different Al-precursors were prepared by sol-gel methods and the dielectric strengths and leakage currents of the materials were investigated. The best performance was found in SrTiO3 films doped with Al2O3 nanoparticles (nano-Al2O3). When 5 mol% of nano-Al2O3 was added to SrTiO3 films with Al electrodes, the dielectric strength was enhanced to 506.9 MV/m compared with a value of 233.5 MV/m for SrTiO3 films. The energy density of the 5 mol% nano-Al2O3 doped SrTiO3 films was 19.3 J/cm3, which was also far higher than that of the SrTiO3 films (3.2 J/cm3). These results were attributed to interfacial anodic oxidation reactions, which were experimentally confirmed by cross-sectional transmission electron microscope studies and theoretically modelled based on Faraday's laws. The films with added nano-Al2O3 featured many conducting paths at the interfaces between the host phase and the guest nano-Al2O3, which promoted ion transport and contributed to the strong anodic oxidation reaction capability of the 5 mol% nano-Al2O3 doped SrTiO3 films.