High conductivity of La2Zr2O7 nanofibers by phase control

Abstract

We report an oxygen ionic conductivity of 0.016 S cm⁻¹ in La₂Zr₂O₇ nanofibers at 500 °C, which is ∼400 times higher than traditional La₂Zr₂O₇ bulk materials. The highly enhanced conductivity of our La₂Zr₂O₇ nanofibers can mainly be attributed to a novel mixed phase structure. We found that a defect fluorite to pyrochlore phase transition occurred at 875 °C. By precise control of calcination conditions, we successfully tuned the ratio of defect fluorite and pyrochlore phases, and further demonstrated that nanofibers with a mixed phase structure have higher conductivity due to an interface lattice mismatch between the two phases. The remarkably high conductivity and facile manufacturing of the La₂Zr₂O₇ nanofibers make them a promising material for high performance SOFCs and oxygen sensors. Moreover, our study provides a new strategy to design solid electrolytes with high conductivity by phase control.