Development and characterization of ScSZ-SDC composites electrolytes for intermediates temperature solid oxide fuel cells

Abstract The use of samarium-doped ceria (SDC) and scandia-stabilized zirconia (ScSZ) has attracted growing attention due to their high ionic conductivity and structural stability at intermediate operating temperatures. In this study, a series of ScSZ–SDC composite electrolytes was developed with the aim of identifying the composition that provides the best balance between structural compatibility, thermal expansion matching, and electrochemical performance for IT-SOFC applications. Three formulations containing 70:30, 80:20, and 90:10 wt ratios of ScSZ to SDC were prepared through wet ball milling, followed by calcination to encourage phase formation. The crystalline phases were examined using X-ray diffraction (XRD) to determine compatibility between the two oxide systems. Thermal expansion coefficient (TEC) measurements were performed to assess matching with IT-SOFC operating conditions. Morphological observations provided insight into the microstructural features of the powders. Electrochemical performance was evaluated using electrochemical impedance spectroscopy (EIS) at temperatures of 800 °C, 700 °C, and 600 °C. XRD analysis confirmed that all compositions crystallized into single-phase cubic fluorite structures, with no secondary phases detected after calcination, indicating good chemical compatibility between ScSZ and SDC. TEC measurements revealed that the 90 wt% ScSZ-10 wt% SDC sample exhibited the most favorable thermal expansion matching for IT-SOFC applications. Notably, this composition also delivered the lowest area-specific resistance, achieving an ASR value of 1.73 Ω cm 2 at 800 °C, and consistently showed the best electrochemical performance across all test temperatures. These findings demonstrate that careful compositional selection of ScSZ-SDC electrolytes is essential for achieving both structural stability and enhanced ionic transport in IT-SOFCs. Among the tested formulations, the 90:10 wt% ScSZ-SDC composition emerged as the most promising, offering an optimal combination of phase compatibility, thermal expansion behaviour, and electrochemical performance.