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Formation, structure and magnetism of the metastable defect fluorite phases AVO3.5+x (A=In, Sc)
Authors:Shahid P Shafi  Rylan J Lundgren  Lachlan MD Cranswick  Mario Bieringer  
Institution:aDepartment of Chemistry, University of Manitoba, Winnipeg, MB, Canada R3T 2N2;bCanadian Neutron Beam Centre, National Research Council Canada, Chalk River Laboratories, Chalk River, ON, Canada K0J 1J0
Abstract:We report the preparation and stability of ScVO3.5+x and the novel phase InVO3.5+x. AVO3.5+x (A=Sc, In) defect fluorite structures are formed as metastable intermediates during the topotactic oxidation of AVO3 bixbyites. The oxidation pathway has been studied in detail by means of thermogravimetric/differential thermal analysis and in-situ powder X-ray diffraction. The oxidation of the bixbyite phase follows a topotactic pathway at temperatures between 300 and 400 °C in air/carbon dioxide. The range of accessible oxygen stoichiometries for the AVO3.5+x structures following this pathway are 0.00less-than-or-equals, slantxless-than-or-equals, slant0.22. Rietveld refinements against powder X-ray and neutron data revealed that InVO3.54 and ScVO3.70 crystallize in the defect fluorite structure in space group Fm-3 m (227) with a=4.9863(5) and 4.9697(3)Å, respectively with A3+/V4+ disorder on the (4a) cation site. Powder neutron diffraction experiments indicate clustering of oxide defects in all samples. Bulk magnetic measurements showed the presence of V4+ and the absence of magnetic ordering at low temperatures. Powder neutron diffraction experiments confirmed the absence of a long range ordered magnetic ground state.
Keywords:Defect fluorite structure  Bixbyite structure  Topotactic oxidation  In-situ X-ray diffraction  Thermal analysis  Powder neutron diffraction  InVO_(3  5+x)  ScVO_(3  5+x)  Low temperature magnetism
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