In situ X-ray diffraction studies during hydrothermal synthesis of ferroelectric materials

Ferroelectric materials are an essential part of our technological society because of their dielectric and piezoelectric properties being utilized in capacitors, sensors and actuators. Nanostructured ferroelectric materials are important for the further development of ferroelectric random-access memory (FeRAM), sensors and actuators in microelectromechanical systems (MEMS), energy-harvesting devices and photocatalysis. Hence, there is a wide range of possible applications for nanostructured ferroelectric materials, meriting further investigations into the synthesis of these materials. Hydrothermal synthesis stands out as one of the most promising synthesis routes for producing nanostructured ferroelectric materials. Hydrothermal synthesis have the potential for being a cheap, low temperature process yielding high quality materials with controlled size, morphology, composition and even self-assembled hierarchical nanostructures. However, controlled design of synthesis parameters is currently limited to a trial-and-error process and chemical intuition, due to a lack of fundamental understanding of the nucleation and growth processes.

In this talk, I will present my work revealing (some of) the formation mechanisms of nanosized and nanostructured ferroelectric materials from hydrothermal synthesis by the use of in situ synchrotron X-ray diffraction. I will present my work on the perovskite BaTiO₃ where the effect of two different titanium precursors were compared. In addition, the development of a new hydrothermal synthesis route for making the tetragonal tungsten bronze SrxBa1-xNb2O6, and how both composition and morphology of the final product could be tuned by simple means, will be presented. Finally, I will try to draw some conclusions of the achievements of the “in situ hydrothermal community”. After all, the year 2020 marks the 30-year anniversary of the first in situ study during hydrothermal synthesis! Have we in these 30 years achieved a (more) fundamental understanding of the nucleation and growth mechanisms?