Under ambient conditions
and in aqueous environments, transformations
of nanoparticle-based ferroelectric components can raise important
stability issues that are relevant for applications as multilayer
capacitors, flexible piezoelectrics, or biomedical devices. We show
that X-ray amorphous BaTiO3 nanoparticles that were grown
by flame spray pyrolysis and which can be incorporated into electrospun
polymer fibers undergo incongruent Ba2+ dissolution in
the presence of water. At pH > 5 and in contact with air, corresponding
Ba solutes spontaneously convert into crystalline BaCO3 needles to produce characteristic nano- and microstructures. We
compared the reactivity of amorphous BaTiO3 nanoparticle
powders with those of nanocrystals after annealing-induced crystallization.
The stability of aqueous nanoparticle–polymer formulations,
which are typically part of nanoparticle encapsulation in polymers
and electrospinning, was included in this analysis. Nanoparticle size,
crystallinity, surface area, the presence of carbonaceous surface
contaminants, and the effect of surface passivation with polymers
are addressed to underline the critical role of condensed water during
the synthesis, storage, and processing of BaTiO3 nanoparticle-based
composites.