Property Study of La_(2-x)Sr_xNiO_4 (x ≤ 0.8) For IT-SOFCs Cathode

摘要

Materials with Ruddlesden-Popper structure (A_2BO_4) such asLa_2NiO_4 system have been identified as the new cathode materialsfor intermediate temperature solid oxide fuel cells (IT-SOFCs) astheir coefficient of thermal expansion values match those of thecurrently used electrolytes. Moreover, such materials have shownmixed ionic and electronic conductivity desirable for cathodes. Thelow electronic conductivity of La_2NiO_4 remains a challenge. Toimprove this property, investigations on La_(2-x)Sr_xNiO_(4+δ) (x = 0, 0.4,and 0.8) prepared via sol-gel and solid state reaction processeswere carried out in this study. Effects of Sr substitution on A siteson physical and electrical properties of the compound wereinvestigated and compared. A simple preparation sol-gel process,carried out at room temperature and using water as solvent for thesynthesis of La_(2-x)Sr_xNiO_(4+δ), was successfully developed. The solgelsynthesis method yielded more homogenous samples withhigher conductivity compared to those synthesized via the solidstate reaction method. Conductivity as high as 160 S/cm at 500°Cwas observed for La_(1.2)Sr_(0.8)NiO_(4+δ) synthesized via the sol-gelprocess.