Facile conversion of layered ruddlesden-popper-related structure y ₂O₃-doped Sr₂CeO₄ into fast oxide ion-conducting fluorite-type y₂O₃-doped CeO₂

The present work shows a new solid- and gas-phase reaction technique for the preparation of a fast oxide-ion-conducting Y₂O₃-doped Ce_1-x-Y_xO_2-δ (x = 0.1, 0.2) (YCO), which involves the reaction of layered (Ruddlesden-Popper K₂NiF ₄-type) structure Y₂O₄-doped Sr ₂CeO₄ (YSCO) with CO₂ at an elevated temperature and subsequent acid- washing. A powder X-ray diffraction study revealed the formation of a single-phase cubic fluorite-type YCO for the CO ₂-reacted and subsequent acid-washed product. Energy dispersive X-ray analysis showed the absence of Sr in the CO₂-treated and subsequent acid-washed product, confirming the transformation of layered YSCO into YCO. The cubic lattice constant was found to decrease with increasing Y content in YCO, which is consistent with the other YCO samples reported in the literature. The scanning electron microscopy study showed smaller-sized particles for the product obtained after CO₂- and acid-washed YCO samples, while the high-temperature sintered YCO and the precursor YSCO exhibit larger-sized particles. The bulk ionic conductivity of the present CO₂-capture- method- prepared YCO exhibits about one and half orders of magnitude higher electrical conductivity than that of the undoped CeO₂ and was found to be comparable to those of ceramic- and wet-chemical-method synthesized rare- earth-doped CeO₂.