Synthesis of homogeneous Ca0.5Sr0.5FeO2.5+δ compound using a mirror furnace method

Graphical abstract: X-ray diffraction pattern indexing of Ca0.5Sr0.5FeO2.5+δ powder sample obtained by mirror furnace method after thermal treatment. Highlights: ► A homogenous compound Ca0.5Sr0.5FeO2.5+δ has been synthesized for the first time by a mirror furnace method. ► Ca0.5Sr0.5FeO2.5+δ powder sample is perfectly homogenous, confirmed by X-ray diffraction, Raman spectroscopy and EDS technique. ► The thermal treatment of Ca0.5Sr0.5FeO2.5+δ powder sample can increase their average grain sizes. -- Abstract: A new synthesis method using melting zone technique via the double mirror furnace around 1600 °C is used to obtain homogenous brownmillerite compounds Ca1−xSrxFeO2.5+δ in the range 0.3 ≤ x ≤ 0.7. These compounds play important role in understanding the mystery of the oxygen diffusion in the perovskite-related oxides. We have successfully solved the miscibility gap problem by synthesizing a good quality of homogenous powder samples of Ca0.5Sr0.5FeO2.5+δ compound. Our result was confirmed by X-rays diffraction, Raman spectroscopy and energy dispersive spectroscopy analysis. Thermal treatment was also applied until 800 °C under vacuum to confirm again the homogeneity of powder samples, improve its quality and show that no decomposition or return to form Ca- and Sr-enriched microdomains takes place as a result of phase separation.