Solid oxide fuel cell devices (SOFCs) become a promising application to generate, or convert, energy in an environmentally friendly and efficient way. However, the use of conventional electrolyte materials like yttria stabilized zirconia require operating temperatures of 800-1000°C to provide sufficient ionic conductivity. Numerous studies in recent years showed that rare earth-doped ceria ceramics may lower the operating temperatures to as low as 500°C, which would significantly improve the economical feasibility of SOFCs. Gadolinium-doped ceria (GDC) is not only among the most studied and promising electrolyte materials for SOFCs, but is also of wide interest for thermal barrier coating (TBC) applications. Thus, a financially attractive production of widely available high grade GDC powders is crucial for future innovation in these fields of application. 
In this study, we present our initial results on GDC (10-20 mol% Gd2O3) produced via different production routes: i) fusion of oxides via electric arc fusion and induction kiln ii) solid-state sintering of Gd₂O₃ and CeO₂, iii) co-precipitation from Gd- and Ce-nitrates, and iiii) sol-gel (Pechini) method. The respective products are crushed and ground to submicron powders and analyzed with X-ray diffraction, scanning electron microprobe, and X-ray fluorescence. The isostatically pressed discs are then tested for microstructure, density and fracture toughness and submitted for ionic conductivity measurements with impedance microscopy. Additionally, we discuss challenges concerning the fusion process and reduction-oxidation reactions from cerium oxide. In conclusion, we provide a direct comparison of GDC products from different production routes.