Preparation of Bismuth Mixed Oxides by Thermal Decomposition of Metallo-Organic Precursors

The metallo-organic precursors of formula MBi(OH)(L-C4H2O6)·nH2O (M = Ca, Sr, Ba; n = 2, 2, 3, respectively) have been obtained via humid synthesis. The obtained samples were amorphous, thus their characterization was performed by Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). The oxygen atoms of the ligand were coordinated simultaneously to the alkaline-earth and the bismuth atoms. During the decomposition of the precursors, several intermediate species were detected, including Bi2O3 and MCO3 (M = Ca, Sr, Ba). After the thermal treatment, the Ca–Bi, Sr–Bi, and Ba–Bi precursors yielded the formation of Ca4Bi6O13, Sr2Bi2O5, and BaBiO3, respectively. The synthesis using this method allowed the formation of these oxides at lower temperatures (Ca4Bi6O13 at 700°C, Sr2Bi2O5 at 700°C, and BaBiO3 at 600°C) and shorter reaction times than the traditional ceramic method.