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.