Route to achieving perfect B-site ordering in double perovskite thin films

Double perovskites (DP, A$_2$BB’O$_6$) exhibit a breadth of multifunctional properties with a huge potential range of applications, including magneto-optic and spintronic devices. However, spontaneous cation ordering is limited by the similar size and charge of B and B’ cations. We introduce a route to stimulate B-site rock-salt ordering. By growing thin films on (111)-oriented substrates, ‘in-plane’ strain acts on the intrinsically tilted oxygen octahedra of the DP and produces two different B-site cages (in size and shape), stimulating spontaneous cation ordering. For the ferromagnetic insulator La$_2$CoMnO$_6$, clear Co/Mn ordering was achieved by growing on (111)-oriented substrates. The difference in B-site cages was further enhanced when grown under minor (111) in-plane compressive strain, resulting in long-range ordering with a saturation magnetization of 5.8 μB/formula unit (f.u.), close to the theoretical 6 μB/f.u., without antiferromagnetic behavior. Our approach enables the study of many new ordered DPs which have never been made before.This work was supported by the European Research Council (ERC) (Advanced Investigator grant ERC-2009-AdG-247276-NOVOX), the EPSRC (Equipment Account Grant EP/K035282/1) and the Isaac Newton Trust (Minute 13.38(k)). LJ thank the support of the European Union Seventh Framework Programme under Grant Agreement 312483—ESTEEM2 (Integrated Infrastructure Initiative-I3). SuperSTEM is the UK National Facility for Aberration Corrected STEM funded by EPSRC

Facile sol-gel molten salt synthesis of double perovskite La 2NiMnO6 as an electrocatalyst for oxygen evolution reactions

Double perovskites have attracted a great attention recently for its high intrinsic activity in oxygen evolution reaction (OER) in electrochemical energy storage and conversion systems in alkaline media. In this study, we are the first to report the new approach of La2NiMnO6 double perovskite which was synthesized via Sol-gel molten-Salt synthesis method. However their stability and specific activity remain challenging that need to be addressed to meet the reqiurement for OER activities. Here in this study we synthesized three different samples with varying concentrations by taking molten salts NaNO 3 and KNO3 in (1:1) ratio such as 30:30, 60:60, 90:90. These samples were then charecterized for phase purity by x-ray diffraction, scanning electron microscopes and electrochemical performances. More importantly electrochemical performance were carefully studied. The stability studies were studied by using cyclic voltammogram for multiple cyclings and their tafel slopes determine the electrochemical reaction to the overpotential. Due to magnetic properties allow these compounds as excellent candidates for various applications such as sensors, photovoltaics, memory devices and radio frequency filters

Synthesis, structure and properties of some transition metal oxides

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