Local Immiscibility Control on Shape and Size of Nano-Objects in Solvo-Thermal Process: Implications for Ferroelectric Nano-Particles

Christine Bogicevic (1) , Pierre-Eymeric Janolin (1)

1 SPMS - Laboratoire Structures, Propriétés et Modélisation des solides

Solvo-thermal synthesis is an effective method to obtain ferroelectric nano-particles. The morphology and size of these nano-particles dramatically impact the dielectric, ferroelectric, piezoelectric, optical properties of these materials at the nanoscale. This is of primary importance for miniaturized electro-active devices based on these materials. Herein, we propose to harness the full potential of water-ethanol mixture solvents to control the shape and size of nano-particles of a model ferroelectric, barium titanate. To take advantage of the local inhomogeneities that exist even in fully miscible liquids such as water and ethanol, we use a barium precursor that is only soluble in water together with a titanium precursor that is present in both components. Indeed, ethanol having hydrophilic and hydrophobic parts the two liquids remain distinct at the local scale. A threshold molar fraction exists at x EtOH =0.3 in water-ethanol mixtures; below this threshold, the water H-bonds network percolates throughout the sample whereas above water forms clusters that act as "nano-reactors". If below the concentration 1 threshold SEM images reveal that only elongated shapes (at best mixed with nanospheres) are obtained, just above the threshold, nano-tori and nano-cubes are observed; even further above the threshold, the reaction is limited to the aggregation-nucleation stage and only nano-cubes are obtained. This illustrates the fact that, in solvo-thermal syntheses, when the solvent is a mixture and one the reactant is confined in one of the constituents of the solvent, it is possible to control the morphology and size of the synthesized nano-objects.

Keywords: nano-objects; solvo-thermal synthesis; hydrothermal synthesis; solvent; ferroelectrics

Domains: Chemical Sciences

Christine Bogicevic, Pierre-Eymeric Janolin. Local Immiscibility Control on Shape and Size of Nano-Objects in Solvo-Thermal Process: Implications for Ferroelectric Nano-Particles. ACS Applied Nano Materials, 2020, ⟨10.1021/acsanm.0c02010⟩. ⟨hal-03023025⟩