화학공학소재연구정보센터
Inorganic Chemistry, Vol.59, No.5, 3026-3033, 2020
Evidence of Paracrystalline Cation Order in the Ruddlesden-Popper Phase LaSr3NiRuO8 through Neutron Total Scattering Techniques
Cation ordering in perovskite-derived phases can lead to a wealth of tunable physical properties. Ordering is typically driven by a large difference between the cation size and charge, but many Ruddlesden-Popper phases A(n+1)B(n)O(3n+1) appear to lack such B-site ordering, even when these differences are present. One such example is the "double" Ruddlesden-Popper n = 1 composition LaSr3NiRuO8. In this material, a lack of B-site ordering is observed through traditional crystallographic techniques, but antiferromagnetic ordering in the magnetism data suggests that B-site cation ordering is indeed present. Neutron total scattering, particularly analysis of the neutron pair distribution function, reveals that the structure is locally B-site-ordered below 6 angstrom but becomes slightly disordered in the midrange structure around 12 angstrom. This provides evidence for paracrystalline order in this material: cation ordering within a single perovskite sheet that lacks perfect registry within the three-dimensional stack of sheets. This work highlights the importance of employing a structural technique that can probe both the local and midrange order in addition to the crystallographic structure and provides a structural origin to the observed magnetic properties of LaSr3NiRuO8. Further, it is proposed that paracrystalline order is likely to be common among these layeredtype oxides.