Anion order in perovskite oxynitrides

Abstract

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(O0.5N0.5) partial anion order (up to at least 750 °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. Oxynitrides of transition metals are emerging materials with useful properties and improved stability over corresponding nitrides, but a full understanding of their anion ordering has been lacking. Now, a neutron and electron diffraction study of the perovskites SrNbO2N and SrTaO2N reveals the chemical principles for anion order and their potential influence on materials properties.

Cite this article

Yang, M., Oró-Solé, J., Rodgers, J. et al. Anion order in perovskite oxynitrides. Nature Chem 3, 47–52 (2011). https://doi.org/10.1038/nchem.908

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