Fast firing of bismuth doped yttria-stabilized zirconia for enhanced densification and ionic conductivity

Abstract

Highly homogeneous bismuth doped cubic-YSZ was prepared using reverse-strike co-precipitation from nitrates. The dopant reduced the sintering temperature for effective fabrication of fully dense pellets within 5 min using fast firing procedure at 1300°C. Delta-Bi2O3 second phase was observed at the boundaries and caused enhancement of grain boundary conductivity, while decreasing activation energy for bulk transport. Longer sintering times (up to 4 h) lead to grain boundary cleaning by evaporation of the Bi phase, consequently reducing the grain boundary conductivity and making the bulk transport activation energy similar to undoped YSZ. No changes in polymorphism were observed during the various processing steps, and only cubic polymorph existed. The findings are expected to have positive impacts on the strategies for manufacturing of more efficient solid oxide fuel cells (SOFC).