Power generating property of sofc using La(Sr)Ga(Mg,Fe)O₃ electrolyte coated with LaGaO₃ film

Oxide ion conductivity in La(Sr)Ga(Fe,Mg)O₃ was investigated in this study and it was found that the oxide ion conductivity much improved by doping Fe into Ga site. Although the electrical conductivity monotonically increased with increasing amount of Fe, partial electronic conduction became significant. Considering the transport number of oxide ions and conductivity, the optimum composition for oxide ion conductivity in this system is La _0.7Sr_0.3Ga_0.7Fe_0.2Mg _0.1O_3-δ (LSGFM73721). Although transport number of oxide ions is almost 0.8, extremely high power density was achieved by using LSGFM73721 as electrolyte of a SOFC. The maximum power densities of 870 and 167 mW/cm² were obtained at 1073 and 873 K, respectively, in spite of 0.5 mm thickness when 90Ni10Fe was used for the anode. A coating of La _0.9Sr_0.1Ga_0.8Mg_0.2O₃ film on anode side of LSGFM plate was investigated by pulsed laser ablation method. Since the deposited film was not dense, open circuit potential was almost unchanged in spite of LSGM film deposition, however, power density improved much by deposition of LSGM film and the maximum power densities of 197 and 100 mW/cm² were achieved at 873 and 773 K respectively. This study reveals that LSGMF is a suitable electrolyte for intermediate temperature SOFCs.