Facile conversion of layered Ruddlesden-Popper-related structure Y2O3-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 Y(2)O(3)-doped Ce(1-x)Y(x)O(2-delta) (x = 0.1, 0.2) (YCO), which involves the reaction of layered (Ruddlesden-Popper K(2)NiF(4)-type) structure Y(2)O(3)-doped Sr(2)CeO(4) (YSCO) with CO(2) 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 CO(2)-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 CO(2)- 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 CO(2)-capture-method-prepared YCO exhibits about one and half orders of magnitude higher electrical conductivity than that of the undoped CeO(2) and was found to be comparable to those of ceramic- and wet-chemical-method synthesized rare-earth-doped CeO(2).