Preparation and characterization of La_0.8Sr_0.2MnO_3-δ cathode for SOFCs fabricated using azeotropic distillation method

Strontium doped lanthanum manganite (LSM) powders were synthesized by three different routes: azeotropic distillation, sol-gel and solid state reaction respectively. The LSM samples, made by azeotropic distillation and sol-gel methods were prepared by firing at 1000°C for 6 h, and the LSM sample, made by solid state reaction method was produced by sintering at 1400°C for 18 h. The samples were characterized by XRD, TEC, SEM, EIS and polarization performance analysis. The results show that all the samples made by different methods have pure orthorhombic LSM phase, however exhibit different micro structure and electrochemical characterization, which relates to the different synthesis methods. The solid state reaction method produces the samples with larger particle size compared with azeotropic distillation and sol-gel methods. The powders made by azeotropic distillation method have less agglomerated particles compared with that made by sol-gel method because the precursor in the former is dispersed in n-butanol before sintering. The polarization current density of powder made by azeotropic distillation method was twice of that made by sol-gel method and four times of that made by solid state reaction method. The values of polarization resistance (R_p) are 0.35 Ω·cm² for the cathode synthesized by azeotropic distillation route, which is much lower than sol-gel (1.5 Ω·cm²) and solid state reaction (2.3 Ω·cm²) at 800°C.