| Perovskite-based oxides like BaTiO3, SrTiO3, and BaxSr1--xTiO 3 are extremely useful materials which possess fundamental properties such as high dielectric constants, high energy densities, and low loss tangents. In addition, perovskites display size, composition, and synthesis dependent dielectric properties. As such, they have found themselves at the forefront of modern capacitive and charge storage applications. While promising, such materials are typically prepared at high temperatures (>500 °C), are extremely brittle, and cannot be easily incorporated into flexible devices. In order to overcome the limitations associated with the processing of high permittivity ceramics, researchers have sought to use a nanocomposite approach, whereby small, well-defined perovskite nanocrystals are integrated into a polymer matrix. In this approach, the polymer provides processability and high breakdown strength (Ebd), while the perovskite filler delivers improved dielectric performance. With this in mind, we developed a low temperature route to preparing gram-scale quantities of small (<15 nm), well-defined BaTiO3, SrTiO3, and BaxSr 1--xTiO3 nanocrystals and blended them into novel polymeric systems. Through precise control of the nanocrystal composition and surface chemistry, it was possible to better understand what factors govern the dielectric performance of the nanocrystals. Compositionally, the dielectric constant of the nanocrystal can be increased by more than an order of magnitude, while controlled surface modification enhances dispersion and improves dielectric temperature and frequency stability. This information was then used to prepare novel composite systems with enhanced performance. |
