Ordered aggregated BaTiO₃ nanocubes with a narrow size distribution were obtained in an aqueous process by using bis(ammonium lactate) titanium dihydroxide (TALH) as Ti source in the presence of oleic acid and tert-butylamine. Kinetics of the formation of BaTiO₃ nanocubes indicated that an in situgrowth mechanism was dominant and the superlattice of nanocubes formed in situ through the growth of BaTiO₃ nanoparticles in Ti-based hydrous gel. The size and morphology of nanocubes were controlled by tuning the concentration and molar ratio of surfactants. A novel growth model dependant on the structure of Ti precursor for the formation and morphology control of BaTiO₃ nanocubes and their superlattice was demonstrated.

SrTiO₃ nanocubes were synthesized in aqueous solution with Bis (ammonium lactate) titanium dihydroxide (TALH) as the Ti source under hydrazine-assisted hydrothermal condition. The SrTiO₃ nanocubes grew from the Ti-based sol through a dissolution-precipitation process and large cubic particles formed through the oriented aggregation of nanocubes over a long time. The morphology, monodispersibility, and size of the nanocubes were controlled through the concentration and ratio of oleic acid and hydrazine.

Orderly assemblies of BaTiO₃ (BT) nanocubes, SrTiO₃ (ST) nanocubes and BT-ST mixture nanocubes were fabricated on Pt-coated Si substrate directly by solution self-assembly and heated at 850 °C. The dielectric nanocubes aligned face to face in a quite wide region of several tens of square-micrometers with a height of one micrometer, and even inside of the structures was ordered. The piezoresponse of BT-ST mixture assembly showed non-linear curve and stepwise behavior at high poling field, which differed from ferroelectric BT and paraelectric ST nanocube assemblies.

Nanocrystals, especially with an anisotropic shape such as cubic, are candidates as 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 CeO2, BaTiO3 and SrTiO3 nanocubes and the ordered assemblies. The importance of shape as well as size distribution is clarified for the bottom-up development of 3D fine structures. CeO2 nanocube assemblies with enhanced surface of specified crystal planes such as (100) and (111) would open new surface-dominant devices. BaTiO3 and SrTiO3 nanocubes with narrow size distributions and robust diversity in compositions were obtained. 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. The supracrystal films exhibited distinct ferroelectric behaviors

Ordered assembly thin films of BaTiO₃ (BT) nanocubes were fabricated on various Pt-coated substrates by dip-coating self-assembly and sintered at 850 °C. BT nanocubes aligned face-to-face in a wide region about 20 µm² with a height of about 600 nm. The thickness of the assembly film was able to be controlled by changing the density of the BT nanocube dispersed solution. The local microstructure of the nanocube assembly was observed by high-resolution transmission electron microscopy. It is revealed that the nanocubes were conjugated face-to-face without grain growth. The piezoresponse properties of BT nanocube assembled films on various substrates were investigated by scanning probe microscopy with a relatively high-force-constant cantilever. The relations between piezoelectric constant and electrical field showed ferroelectric hysteresis loops with high rectangularity.