Inverse size-dependence of piezoelectricity in single BaTiO3 nanoparticles

The piezoelectric charge coefficients d33 of single BaTiO3 (BT) nanoparticles (NPs) were characterized using a transmission electron microscope (TEM) that is equipped with a precise charge meter and an in-situ TEM indentation holder that enables controlled compression experiments. An exceptionally high d33 of 1775 pC/N was obtained in NPs that are smaller than the critical diameter (D; typically known as < 100 nm) that has been regarded as the lower limit to permit for ferroelectricity in BT. The mechanical conversion efficiency of piezoelectric BT nanogenerators enhanced as D of BT NPs was decreased; this result corresponds with the single-NP compression measurements of d33. This quantification of the effect of D in ferroelectric materials may guide development of efficient and high-powered nanostructured piezoelectric energy devices such as piezoelectric nanogenerators.