Synthesis, Phase Formation and Characterization of Co_4Nb_2O_9 Powders Synthesized by Solid-State Reaction

摘要

A corundum-type structure of cobalt niobate (Co_4Nb_2O_9) has been synthesized by a solidstate reaction. The formation of the Co_4Nb_2O_9 phase in the calcined powders was investigated as a function of calcination conditions by differential thermal analysis (DTA) and X-ray diffraction (XRD) techniques. Morphology and particle size have been determined by scanning electron microscopy (SEM). It was found that the minor phases of unreacted Co_3O_4 tend to form together with the columbite CoNb_2O_6 phase at a low calcination temperature and short dwell time. It seems that the single-phase of Co_4Nb_2O_9 in a corundum phase can be obtained successfully at the calcination conditions of 900°C for 60 min, with heating/cooling rates of 20°C /min.