posted on 2021-03-30, 16:39authored byKristine Bakken, Viviann H. Pedersen, Anders B. Blichfeld, Inger-Emma Nylund, Satoshi Tominaka, Koji Ohara, Tor Grande, Mari-Ann Einarsrud
Carbonate formation
is a prevailing challenge in synthesis of BaTiO3, especially
through wet chemical synthesis routes. In this
work, we report the phase evolution during thermal annealing of an
aqueous BaTiO3 precursor solution, with a particular focus
on the structures and role of intermediate phases forming prior to
BaTiO3 nucleation. In situ infrared spectroscopy, in situ X-ray total scattering, and transmission electron
microscopy were used to reveal the decomposition, pyrolysis, and crystallization
reactions occurring during thermal processing. Our results show that
the intermediate phases consist of nanosized calcite-like BaCO3 and BaTi4O9 phases and that the intimate
mixing of these along with their metastability ensures complete decomposition
to form BaTiO3 above 600 °C. We demonstrate that the
stability of the intermediate phases is dependent on the processing
atmosphere, where especially enhanced CO2 levels is detrimental
for the formation of phase pure BaTiO3.