Influence of Sintering Additive on the Electrical Conductivity, Chemical Stability and Sinterability of BaCe0.55Zr0.3Y0.15O3-δ

Friday, 31 July 2015: 15:20
Boisdale (Scottish Exhibition and Conference Centre)
H. An (Korea Institute of Science and Technology), D. Shin (Hanyang University), S. M. Choi, J. Hong, K. J. Yoon, J. W. Son, B. K. Kim, and J. H. Lee (Korea Institute of Science and Technology)
Ceramic proton conductors have regarded as an electrolyte materials for the next-generation intermediate-temperature solid oxide fuel cell (IT-SOFC) due to their lower activation energy than oxygen ion conductor in its operating condition. Among those candidates, Ba based perovskite-structured materials such as Yttrium doped BaCeO3 and BaZrO3 are frequently used because of their high proton conductivity. In addition, a discovery of BaCeO3-BaZrO3 solid solution (BCZYs) providing an acceptable compromise between chemical stability and proton conductivity consolidates its recognition as a promising electrolyte material. However, due to the refractory nature of BCZYs, a detrimental in electrical conductivity caused by an inevitable barium deficiency from the high temperature sintering, prohibits its practical utilization, and thus, many of studies were devoted to reduce sintering temperature of BCZYs. Recently it was reported that, even though the exact mechanism was not understood yet, the addition of some transition metal oxide such as nickel oxide, zinc oxide and copper oxide gives a tremendous enhancement in sintering of BCZYs. Moreover, sintering aid-assisted sintered BCZYs have some similarity in resulting feature such as reduced bulk electrical conductivity and enhanced chemical stability which has been expected due to barium deficiency in BCZYs. Recently, solid state reactive sintering (SSRS) in which synthesis and sintering of BCZYs occurs at the same time by employing nickel oxide as a sintering aid, was reported. According to their study, barium deficiency was induced by the formation of barium-transition metal compound (BaY2NiO5) consequently acting as a sintering aid during sintering. Therefore, addition of extra sintering aid with a form of BaY2NiO5 on BCZYs is supposed to be more efficient to prevent barium deficiency. Hence, in order to compare the effect of different form of sintering additives, we investigate the electrical conductivity, chemical stability and sinterability of BaCe0.55Zr0.3Y0.15O3-δ with various types of nickel oxide additives (simple oxide form, NiO and compound form, BaY2NiO5) via dilatometery, DC 4-probe, EIS, XRD and TG/DSC analysis. In this presentation, in addition to the experimental results, possibility and limitation of compound form of sintering aid will be also discussed.