Effects of Milling Speed and Calcination Temperature on the Phase Stability of Ba<sub>0.5</sub>Sr<sub>0.5</sub>Co<sub>0.8</sub>Fe<sub>3-δ</sub>

Abstract

The phase instability of Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) is widely reported in atmospheres containing carbon dioxide, which affects the long term electrochemical performance. The aim of this study is to investigate the phase stability of BSCF under the influence of milling and calcination temperature. Commercial BSCF powder was milled at 200 and 500 rpm and subsequently calcined at 750, 800 and 900 °C. The BSCF samples were characterized by using X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FESEM). Secondary phases that were triggered after milling, however reduced with the increase of calcination temperature up to 800 °C. It was also found that the reduction of crystallite size and particle size at increased calcination temperature might be affected by the removal of these secondary carbonate phases. Moreover, the removal of carbonate was clearly evidenced in FTIR spectra by the reduction of carbonate signal intensities. In brief, a minimum calcination temperature of 900 °C was suggested for successful carbonate removal and recovery of single BSCF phase.