Perovskite　oxide　Ba0.5Sr0.5Co0.8Fe0.2O3-delta　(BSCF)　is　a　highly　active　cathode　material　widely　studied　for　intermediate　temperature　solid　oxide　fuel　cells　(IT-SOFCs),　however,　the　tendency　of　phase　transition　of　BSCF　under　IT-SOFC　operating　conditions　poses　a　critical　challenge　for　its　reliable　applications.　Here,　a　multiphase　BSCFGd0.1Ce0.9O1.95　(GDC)　nanocomposite　with　heterogeneous　interfaces　is　synthesized　at　a　relatively　low　calcination　temperature　of　750　degrees　C.　Both　the　multiphase　composition　and　microstructural　morphology　of　the　nanocomposite　are　very　stable　during　annealing　at　750　degrees　C.　The　unique　multiphase　structure　and　ultrafine　microstructure　of　the　nanocomposite　can　be　maintained　in　the　resultant　cathode　through　a　sintering-free　direct　assembly　fabrication　method.　As　a　consequence,　a　corresponding　single　cell　based　on　the　BSCF-GDC　nanocomposite　cathode　generates　a　maximum　power　density　of　1.41　W　cm(-2)　at　750　degrees　C　with　outstanding　galvanostatic　stability　for　100　h.　This　work　provides　an　effective　means　for　the　design　and　utilization　of　highly　active　BSCF-based　nanocomposite　cathodes　for　durable　IT-SOFCs.