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2019
ACL
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L.Zhou, Y.Han, C.Yin, Y.Wang, X.Yang, M.Allix, Q.Huang, J.Xiong, B.Wang, G.Li, X.Kuang, X.Xing, 'Trigonal-Planar Low-Spin Co2+ in a Layered Mixed-Polyhedral Network from Topotactic Reduction', Inorg. Chem. 58 14193-14203 (2019) doi:10.1021/acs.inorgchem.9b02244
Topotactic reduction of the perovskite oxide
TbBaCo2O5.5 with CaH2 leads to a new crystalline phase
TbBaCo2O4.5, adopting a 2 × 2 × 1 superstructure compared
to TbBaCo2O5.5. The structure consists of a corner-shared
network of square pyramidal CoO5 and trigonal planar CoO3
units. Magnetic susceptibility and variable temperature
neutron diffraction data reveal that TbBaCo2O4.5 adopts a
G-type antiferromagnetically ordered structure (TN ∼ 322 K).
The ordered moments are consistent with the presence of
low-spin Co2+ (S = 1/2) in trigonal-planar coordination and
high-spin Co2+ centers in square pyramidal coordination.
TbBaCo2O4.5 shows lower conductivity than TbBaCo2O5.5,
which is consistent with the p-type conduction behavior. The unique anion vacancy arrangements in TbBaCo2O4.5 further
complement the role of A-cations in controlling the oxygen vacancy distribution in LnBaCo2O5+δ series and demonstrate more
opportunity to tune the structural and physical properties based on cationic and anionic lattice coupling.
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