TY  - JOUR
AU  - Samain, Louise
AU  - Amshoff, Philipp
AU  - Biendicho, Jordi J.
AU  - Tietz, Frank
AU  - Mahmoud, Abdelfattah
AU  - Istomin, Sergey Ya.
AU  - Grins, Jekabs
AU  - Svensson, Gunnar
AU  - Hermann, Raphael
TI  - Crystal structure and high-temperature properties of the Ruddlesden–Popper phases Sr$_{3−x}$Y$_{x}$(Fe $_{1.25}$ Ni$_{0.75}$)O$_{7−δ}$ (0≤x≤0.75)
JO  - Journal of solid state chemistry
VL  - 227
SN  - 0022-4596
CY  - Orlando, Fla.
PB  - Academic Press
M1  - FZJ-2015-02494
SP  - 45 - 54
PY  - 2015
AB  - Ruddlesden–Popper n=2 member phases Sr3−xYxFe1.25Ni0.75O7−δ, 0≤x≤0.75, have been investigated by X-ray and neutron powder diffraction, thermogravimetry and Mössbauer spectroscopy. Both samples as-prepared at 1300 °C under N2(g) flow and samples subsequently air-annealed at 900 °C were studied. The as-prepared x=0.75 phase is highly oxygen deficient with δ=1, the O1 atom site being vacant, and the Fe3+/Ni2+ ions having a square pyramidal coordination. For as-prepared phases with lower x values, the Mössbauer spectral data are in good agreement with the presence of both 5- and 4-coordinated Fe3+ ions, implying in addition a partial occupancy of the O3 atom sites that form the basal plane of the square pyramid. The air-annealed x=0.75 sample has a δ value of 0.61(1) and the structure has Fe/Ni ions in both square pyramids and octahedra. Mössbauer spectroscopy shows the phase to contain only Fe3+, implying that all Ni is present as Ni3+. Air-annealed phases with lower x values are found to contain both Fe3+ and Fe4+. For both the as-prepared and the air-annealed samples, the Y3+ cations are found to be mainly located in the perovskite block. The high-temperature thermal expansion of as-prepared and air-annealed x=0.75 phases were investigated by high-temperature X-ray diffraction and dilatometry and the linear thermal expansion coefficient determined to be 14.4 ppm K−1. Electrical conductivity measurements showed that the air-annealed samples have higher conductivity than the as-prepared ones.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000355639500008
DO  - DOI:10.1016/j.jssc.2015.03.018
UR  - https://juser.fz-juelich.de/record/189316
ER  -