Effect of Surface Modification on the Dielectric Properties of BaTiO3 Nanocrystals

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Abstract
We present the first direct comparison of the dielectric properties of organically modified BaTiO3 nanocrystals with unmodified BaTiO3 nanocrystals. Well-defined 6 nm BaTiO3 nanocrystals were functionalized with n-hexylphosphonic acid (HPA) to give a surface coverage of 2.4 phosphonate groups/nm2. Chemisorption of HPA to the oxide surface occurs mainly via tridentate bonding of the deprotonated phosphonate, as determined by 31P MAS NMR, FT-IR, and XPS spectroscopies. The HPA-modified BaTiO3 (HPA-BaTiO3) nanocrystals possess improved dielectric properties, as demonstrated by decreased sensitivity to temperature and frequency for both the dielectric constant and dielectric loss. HPA-BaTiO3 had a much lower dielectric loss than unmodified BaTiO3, which also indicates an improvement in the dielectric quality of the material. Such improvements are of potential importance for the fabrication of high energy density nanocomposites.

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