Synthesis of nano-crystalline Sm0.5Sr0.5Co(Fe)O3−δ perovskite oxides by a microwave-assisted sol–gel combustion process

Nano-crystalline Sm0.5Sr0.5Co(Fe)O3−δ (SSCF) perovskite oxides were synthesized by a microwave-assisted sol–gel combustion process using glycine as the complexing agent. The properties of the resultant powder were characterized by scanning electron microscopy (SEM), thermo gravimetric-differential thermal analysis (TG-DTA), Brunauer–Emmett–Teller (BET) and X-ray diffraction (XRD) techniques. The synthesis conditions to form the perovskite phase in terms of the glycine/metal-ion molar ratio, the total metal ion concentration in the starting solution and the calcination temperature were investigated and optimized. The experimental results indicated that the glycine/metal-ion ratio should be controlled at about 2 with the starting metal ion concentration of 0.25 mol L−1 and the calcination temperature should be around 800 °C so as to obtain the pure perovskite structure with high economical efficiency. The overall synthesis period of perovskite oxides can be reduced significantly compared to the conventional combustion route. The partial substitution of Fe for Co cations with molar fraction higher than 0.2 could improve noticeably the stability of the perovskite against CO2, but the calcination temperature to obtain pure perovskite phase should be increased.