Enhancing the ionic conductivity of ThO2 ceramics via a samarium doping strategy

The development of ThO 2 -based electrolyte materials with enhanced electrical conductivity is crucial for advancing the high-performance application of ThO 2 . In this study, samarium-doped ThO 2 ceramics with the composition Th 1- x Sm x O 2- x /2 ( x = 0.01–0.2) were synthesized via the positive co-precipitation methods followed by conventional sintering. Their total ionic conductivity was systematically evaluated under high temperatures conditions. The results demonstrate that samarium doping enables the material to retain its cubic fluorite structure, with significantly refining the grain size. With increasing samarium doping content, the lattice parameter exhibits a non-linear variation. Notably, samarium doping not only reduces the ceramic grain size but also enhances the total ionic conductivity, which increased with the samarium doping level. The Th 0.8 Sm 0.2 O 1.9 sample achieved the highest ionic conductivity of 6.4 × 10 −3 S/cm at 800 °C representing a 54 times increase compared to undoped ThO 2 ceramics. This remarkable conductivity enhancement is primarily attributed to grain refinement and the formation of oxygen vacancies induced by samarium doping. The electrochemical performance results confirm the potential of Th 1- x Sm x O 2- x /2 ceramics as candidates for high-temperature electrolyte applications.