Bi2(C2O4)3·7H2O and Bi(C2O4)OH Oxalates Thermal Decomposition Revisited. Formation of Nanoparticles with a Lower Melting Point than Bulk Bismuth

Pierre Roumanille (1, 2) , Valérie Baco-Carles (1) , Corine Bonningue (1) , Michel Gougeon (1) , Benjamin Duployer (1) , Philippe Monfraix (2) , Hoa Le Trong (2) , Philippe Tailhades (1)

1 CIRIMAT - Centre interuniversitaire de recherche et d'ingenierie des matériaux
2 IRT Saint Exupéry - Institut de Recherche Technologique

Two bismuth oxalates, namely, Bi2(C2O4)3·7H2O and Bi(C2O4)OH, were studied in terms of synthesis, structural characterization, particle morphology, and thermal behavior under several atmospheres. The oxalate powders were produced by chemical precipitation from bismuth nitrate and oxalic acid solutions under controlled pH, then characterized by X-ray diffraction (XRD), temperature-dependent XRD, IR spectroscopy, scanning electron microscopy, and thermogravimetric differential thermal analyses. New results on the thermal decomposition of bismuth oxalates under inert or reducing atmospheres are provided. On heating in nitrogen, both studied compounds decompose into small bismuth particles. Thermal properties of the metallic products were investigated. The Bi(C2O4)OH decomposition leads to a Bi−Bi2O3 metal−oxide composite product in which bismuth is confined in a nanometric size, due to surface oxidation. The melting point of such bismuth particles is strongly related to their crystallite size. The nanometric bismuth melting has thus been evidenced ∼40 °C lower than for bulk bismuth. These results should contribute to the development of the oxalate precursor route for low-temperature soldering applications.

Domaines: Chimie inorganique

Pierre Roumanille, Valérie Baco-Carles, Corine Bonningue, Michel Gougeon, Benjamin Duployer, et al.. Bi2(C2O4)3·7H2O and Bi(C2O4)OH Oxalates Thermal Decomposition Revisited. Formation of Nanoparticles with a Lower Melting Point than Bulk Bismuth. Inorganic Chemistry, 2017, 56 (16), pp.9486-9496. ⟨10.1021/acs.inorgchem.7b00608⟩. ⟨hal-02009024⟩