Single step reactive sintering and chemical compatibility between La9Sr1Si6O26.5 and selected cathode materials

Apatite-type silicates are considered as promising electrolytes for solid oxide fuel cells (SOFC). However more studies on the chemical compatibility of these materials with common SOFC electrodes are required. Here, we report the synthesis of single phase La9Sr1Si6O26.5 composition by reactive sintering at 1650 °C for 10 h. Fully dense pellets showed very high oxide-anion conductivity, 25 mS cm−1 at 700 °C. Furthermore, the chemical compatibility of La9Sr1Si6O26.5 with some selected cathode materials has also been investigated. The lowest reaction temperatures were determined to be 1100 °C, 1000 °C and 900 °C for La0.8Sr0.2MnO3−δ, La2Ni0.8Cu0.2O4 and La0.6Sr0.4Co0.8Fe0.2O3, respectively. The segregation of minor amounts of SiO2 seems to be a key limiting factor that must be overcome. Finally, these cathode materials were deposited over dense oxy-apatite pellets and the area specific resistances in symmetrical cells were determined. These values, at 700 °C, were 14.4 and 2.6 Ω cm2 for La0.8Sr0.2MnO3−δ and La0.6Sr0.4Co0.8Fe0.2O3−δ, respectively. Furthermore, the area specific resistances are notably improved 0.6 Ω cm2 when a 50 wt.% composite of La0.6Sr0.4Co0.8Fe0.2O3−δ and Ce0.8Gd0.2O1.9 is used.