Several kinds of bismuth (III) oxalate have been prepared, depending on the experimental conditions during their precipitation. Decomposition of these precursors is followed by CRTA techniques. Under vacuum, the nature of decomposition product depends on the nature of oxalate precursor whereas in air, beta-Bi2O3 oxide is systematically obtained between 250 and 300 degreesC. This beta-Bi2O3 phase is stable from ambient temperature to its transition into alpha-phase near 300 degreesC. Ionic and electronic conductivities of the obtained bismuth (III) oxide is measured by Complex Impedance Spectroscopy between 25 and 820 degreesC.