SINTERING PERFORMANCE OF YSZ CERAMICS WITH TRANSITION METAL OXIDE SINTERING AID

摘要

Transition metal oxides were found to dramatically alter the sintering behavior of micron sized yttria stabilized zirconia at concentrations of 1 mol%. Cobalt, nickel, and chromium oxide yielded enhancement in sintering performance, while copper oxide yielded a detriment to the sintering process. The effects of nickel oxide were examined with the primary goal to reduce the sintering temperature of solid oxide fuel cell electrolyte fabrication. The effects of nickel oxide were evaluated in both partially (3Y) and fully (8Y) stabilized zirconia with 0 to 1 mol% nickel addition, as NiO, and characterized from 1300°C to 1400°C with a 1 hr dwell. Utilizing low temperature 1300°C sintering, 8YSZ powder doped with nickel oxide yielded a density of 95% theoretical, whereas the 3YSZ was more sensitive to the dopant yielding 97% density with the nickel oxide additions. Grain growth for the doped specimens is increased and an early transition to transgranular fracture is noted for the doped specimens. The total ionic conductivity of the doped specimens remained constant, however, the grain boundary contribution showed an improvement from the dopant. Further, ring on ring flexural testing of tape cast electrolytes indicates up to 46% increase in flexural strength from the dopant addition.