Formation of Bim+1Fem-3Ti3O3m+3 (m=4-9) Nanocrystals upon Thermal Decomposition of Coprecipitated Hydroxides

Nanocrystals of Bim+ 1Fem- 3Ti3O3m+ 3 (m = 4-9) Aurivillius phases were synthesized by thermal decomposition of a coprecipitated mixture of bismuth, iron, and titanium hydroxides. The average crystallite size in nanopowders depends on m and is 50-100 nm. The samples were characterized by simultaneous thermal analysis, elemental analysis, X-ray diffraction, and Mossbauer spectroscopy. It was shown that the onset of Bim+ 1Fem- 3Ti3O3m+ 3 crystallization is near the melting point of the bismuth oxide-based non-autonomous (surface) phase (450 degrees C). The Bim+ 1Fem- 3Ti3O3m+ 3 compounds where m <= 5 crystallize in one stage. The compounds where m > 5 are formed in two stages. First, Aurivillius phases with m approximate to 5 and an amorphous phase are formed. Then, the components of the amorphous phase are incorporated into the perovskite-like blocks of the Aurivillius (m approximate to 5) phases, most likely through their outer perovskite-like layers. Then, the components are redistributed between the outer and inner layers of the perovskite-like blocks. The elucidated dependence of the formation mechanism of Bim+ 1Fem- 3Ti3O3m+ 3 nanocrystals on their composition can be used in the technology of directed synthesis of nanocrystalline multiferroics.

Automated summary

The formation mechanism of Bim+ 1Fem- 3Ti3O3m+ 3 nanocrystals depends on their composition, which is crucial for the technology of directed synthesis of nanocrystalline multiferroics.