Formation of Bi2Ca3CO2O9 in the BiO1.5-CaO-CoO system was confirmed by
x-ray diffraction (XRD). Synthetic conditions were optimized to obtai
n phase-pure material by solid-state reaction in air or oxygen. The po
wder XRD data for Bi2Ca3Co2O9 are presented. Formation of neither Bi2C
a2Co1Oy nor Bi2Ca4CO3Oy was observed under the optimal synthetic condi
tions.