期刊
NATURE CHEMISTRY
卷 3, 期 1, 页码 47-52出版社
NATURE PUBLISHING GROUP
DOI: 10.1038/NCHEM.908
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资金
- Ministerio de Ciencia e Innovacion [MAT2008-04587, PR2008-0164]
- Generalitat de Catalunya
- Engineering and Physical Science Research Council
- Science and Technology Facilities Council
- Royal Society
- Chemistry Research School of Edinburgh
- St Andrews Universities
- Leverhulme Trust
Transition-metal oxynitrides with perovskite-type structures are an emerging class of materials with optical, photocatalytic, dielectric and magnetoresistive properties that may be sensitive to oxide-nitride order, but the anion-ordering principles were unclear. Here we report an investigation of the representative compounds SrMO2N (M = Nb, Ta) using neutron and electron diffraction. This revealed a robust 1O/2(O-0.5 N-0.5) partial anion order (up to at least 750 degrees C in the apparently cubic high-temperature phases) that directs the rotations of MO4N2 octahedra in the room-temperature superstructure. The anion distribution is consistent with local cis-ordering of the two nitrides in each octahedron driven by covalency, which results in disordered zigzag M-N chains in planes within the perovskite lattice. Local structures for the full range of oxynitride perovskites are predicted and a future challenge is to tune properties by controlling the order and dimensionality of the anion chains and networks.
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