New strategies for materials fabrication are of fundamental importance in the
advancement of science and technology. Nanocrystals, especially with an
anisotropic shape such as cubic, are candidates for building blocks for new
bottom-up approaches to materials assembly, yielding a functional architecture.
Such materials also receive attention because of their intrinsic size-dependent
properties and resulting applications. Here, we report synthesis and
characteristics of BaTiO3 and SrTiO3 nanocubes and the
ordered assemblies as ferroelectric supracrystals. BaTiO3 and
SrTiO3 nanocubes with narrow size distributions were obtained in
an aqueous process. BaTiO3 films made up of ordered nanocube
assemblies were fabricated on various substrates by evaporation-induced
self-assembly method. Regardless of the substrate, the nanocubes exhibited {100}
orientations and a high degree of face-to-face ordering, which remained even
after heat treatment at 850 °C. Piezoresponse force microscopy was
carried out on the supracrsytal films to obtain plots of the
d33 piezoelectric coefficient against the poling
field, and ferroelectric hysteresis curves were shown.