The YBaCo 4 O 7+ (Y-114) phase has recently attracted interests as a potential oxygen storage material due to its oxygen intake/release capability at 200 ~ 400C.Nevertheless, thermal instability of Y-114 has been an obstacle for future applications, since this compound immediately starts to decompose when the sample is heated at 700 ~ 800C in oxygen-rich atmosphere. Here we demonstrate that Al-for-Co substitution in Y-114 drastically enhances the thermal stability. Substituting only 10 at% of aluminum for cobalt in Y-114 essentially suppresses the decomposition reaction seen at 700 ~ 800C, while well retaining its remarkable oxygen intake/release capability at 200 ~ 400C. It is also revealed that the addition of aluminum effectively reduces the particle size. The Al-substituted Y-114 products exhibit superior oxygen intake/release response to the Al-free products upon switching the atmosphere between O 2 and N 2 .
Crystal structure was refined on Sr - Nb and Sr ( La )- Nb oxynitride perovskites prepared through citrate route by using neutron diffraction. The former had the composition of SrNbO2.11N0.89and crystallized in I4/mcm with a = 0.57099(2) nm , c = 0.81015(5) nm having excess oxide ions in apical 4a site around Nb being compared to the cis- TaO4N2octahedra in SrTaO2N . The latter crystallized in the same space group with Sr0.81La0.19having a = 0.57126(3) nm , c = 0.81055(6) nm . It was assumed that Sr0.81La0.19O1.90N1.10has similar O/N occupancy in both apical 4a and equatorial 8h sites. The La substitution made the O/N occupancies equilibrated around Nb . The niobium valency was slightly less than five in these oxynitride perovskites.
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