Thermal decomposition of sol–gel synthesized bismuth citrate

Abstract

This paper investigates the thermal decomposition of bismuth citrate sol–gel precursors using thermogravimetry, derivative thermogravimetry and differential thermal analysis, as well as Fourier transform infrared spectroscopy and powder X-ray diffraction with Rietveld refinement analysis. Citric acid effectively complexes Bi3+ to form bismuth citrate monohydrate after drying at 100 °C. Upon further heating, dehydration and decomposition of excess citric acid occurs, followed by the decomposition of bismuth citrate to form a mixture of α-Bi2O3 and bismuth oxide acetate at ~ 300 °C. An intermediate bismuth subcarbonate phase was detected upon further heating before final decomposition to Bi2O3. The subcarbonate phase has not been reported in bismuth citrate decomposition studies before. A partial phase transition from α-Bi2O3 to γ-Bi2O3 was also observed after heating to 700 °C and 750 °C.