Investigation of topotactic reduction processes for manganate (n=1) Ruddlesden-Popper phases and scandium vanadate

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Hernden, Brad
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Over the last decade progress towards step-wise structural transformations in solid state chemistry has been made using metal hydride reductants. Alkali and alkali-earth metal hydrides can effectively reduce transition metal oxides resulting frequently in novel oxygen defect structures. This provides access to control over cation oxidation states and magnetic exchange pathways, and thus electronic and magnetic properties. The goal for this research was to investigate a representative system that could be used both for exploration of novel oxygen defect phases and for investigating the fundamental parameters governing successful solid state reductions. The systems chosen for investigation were Sr2-xCaxMnO4 (0<x<2) and Sr2-xBaxMnO4 (x< 0.04). Detailed analysis of metal hydride reactivity with Sr2MnO4 is presented in addition to proof of the solid state reduction mechanism. As a result a number of novel oxygen defect phases have been produced, Sr2MnO4-x (0<x<0.37). The potential for producing novel lithium doped Sr2MnO4-x phases using a reduction/insertion approach with LiH has also been identified. Lastly as a test of application for metal hydrides as reductants the ability to topotactically reduce ScVO4 has been investigated.
manganate, powder x-ray diffraction, insitu diffraction, topotactic, reduction, oxidation, solid state, Ruddlesden-Popper