PVA-assisted synthesis and characterization of nano-crystalline La³⁺ and Mg²⁺ co-doped CeO₂ electrolyte for intermediate-temperature solid oxide fuel cells

A series of nano-crystalline ceria-based solid solution electrolyte, Ce_{0. 8}La_{0. 2-x}Mg_xO_2-δ (x = 0. 0, 0. 05, 0. 10, 0. 15, and 0. 2), were synthesized via the polyvinyl alcohol (PVA) assisted combustion method, and then characterized to the crystalline structure, powder morphology, sintering micro-structure, and electrical properties. Present study showed that Ce_{0. 8}La_{0. 2-x}Mg_xO_2-δ was exceedingly stable as a cubic phase in all temperature range and exhibited fine crystals ranging from 15 to 20 nm. After sintering at 1,400 °C, the as-prepared pellets exhibited a dense micro-structure with 96 % of theoretical density. The electrical conductivity was studied using AC impedance spectroscopy and it was observed that the composition Ce_{0. 8}La_{0. 1} Mg_{0. 1}O_2-δ showed higher electrical conductivity of 0. 020 S cm^-1 at 700 °C. The thermal expansion was measured using dilatometer technique in the temperature range 30-1,000 °C. The average thermal expansion coefficient of Ce_{0. 8}La_{0. 1} Mg_{0. 1}O_2-δ was 12. 37 × 10^-6 K^-1, which was higher than that of the commonly used SOFC electrolyte YSZ (~10. 8 × 10^-6 K^-1).