Low-temperature sintering and microstructure evolution of Bi2O3-doped YSZ

Abstract

Yttria-stabilized zirconia (YSZ) is one of the most common solid electrolyte materials for solid oxide fuel cells (SOFCs). However, the sintering temperature of commercial YSZ powders is usually above 1500℃. In this work, powders with variable amounts (from 1mol% to 12mol%) of bismuth oxide (Bi2O3) were separately added to commercially available yttria partially stabilized zirconia (3YSZ) powders as sintering additives, in order to lower the sintering temperature of the latter. After the addition, the powder mixtures were dry-pressed and sintered at different temperatures between 850℃ and 1200℃. Then, the relative densities, phases and microstructures of the sintered ceramic specimens were analyzed. The results indicated that the addition of Bi2O3 enhanced the sintering activity of 3YSZ, resulting in a 3YSZ material with an extremely low sintering temperature. When the amount of Bi2O3 exceeded 7mol%, the ceramic specimens were densified up to 96.3% by a pressureless conventional sintering process at 850℃ for only 1.5h. Furthermore, Bi2O3 can affect the degree of crystallinity of different phases, such as the tetragonal phase and monoclinic phase in 3YSZ powder.