Low-temperature synthesis of solid-solution BaxSr1-xTiO3 nanocrystals

The very low-temperature synthesis (20-80 degrees C) of sub-15 nm BaxSr1-xTiO3 (0 <= x <= 1) nanocrystals and characterization of their dielectric properties as a function of composition are reported. A series of BaxSr1-xTiO3 nanocrystals were synthesized under ultrabenign conditions (i.e., low temperatures, ambient pressure and neutral pH) using a vapor diffusion sol-gel technique, whereby water is slowly diffused into a mixture of bimetallic alkoxides to yield the solid-solution nanocrystals in quantitative yield on the gram scale. The unsintered 12 nm Ba0.69Sr0.31TiO3 nanocrystals synthesized at 20 degrees C possess a maximized dielectric constant (epsilon' = 341 at 1 kHz) for the solid solution series, and is more than an order of magnitude greater than the dielectric constant for SrTiO3 (epsilon' = 11.0 at 1 kHz). The observed non-monotonic dependence of the dielectric constant on solid solution composition for these small nanocrystals is consistent with theoretical and empirical studies for bulk BaxSr1-xTiO3 ceramics, proving this dielectric effect holds for small nanocrystals.