An investigation of structure and electrical characteristics of lanthanum strontium manganite nanopowders with different Sr2+ ion concentrations

Generally, the efficiency of solid oxide fuel cells is heavily dependent on the electrocatalytic activity of the cathode toward the oxygen reduction reaction. In order to achieve a better cathode performance, La_xSr_1-xMnO₃ (LSM) nanopowders with different Sr²⁺ ion contents varying from 0.2 to 0.8 have been synthesized using the coprecipitation method. The obtained nanoparticles were characterized by x-ray diffraction, field emission scanning electron microscopy, and electrochemical impedance spectroscopy. It was found that the LSM nanoparticles seemed to exhibit high polarization resistance with the increase of the Sr²⁺ ion molar ratios. The crystallite size was found to increase from 16.4 to 24.3 nm with increasing Sr²⁺ content from 0.2 to 0.8. The lattice parameters were decreased with Sr²⁺ ion content which may be caused by an increase in internal stress with the increasing grain size of LSM. Meanwhile, the real part impedance (Z′) was increased from 10 (Ω) at 0.2 Sr²⁺ to 24 (Ω) at 0.8 Sr²⁺ ion ratio. Alternatively, |Z| of prepared sample was increased from 12 to 26 (Ω) by increasing Sr²⁺ ion molar ratios from 0.2 to 0.8.