Understanding the Interplay of Vacancy, Cation, and Charge Ordering in the Tunable Sc2VO5+δ Defect Fluorite System Academic Article uri icon

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abstract

  • We report the synthesis, structure, and redox behavior of the cation-ordered tetragonal Sc2VO5+δ defect fluorite superstructure previously thought to be the oxygen precise A3+2B4+O5 phase. Four synthesis routes in oxidative, reductive, and inert atmospheres are demonstrated. Ex situ and in situ powder X-ray and neutron diffraction analyses reveal vanadium disproportionation reactions. The structure-reaction map illustrates the oxygen-dependent competition between the tetragonal cation and anion ordered Sc2VO5+δ and the disordered cubic Sc2VO5+δ' (δ < δ' ≤ 0.5) phases as a function of temperature. Oxidation states and oxide stoichiometries were determined with DC magnetometry and XANES experiments. The tetragonal cation ordered Sc2VO5+δ phase with δ = -0.15(2) for as-synthesized samples reveals vanadium charge ordering. V3+ and V4+ cations occupy octahedral sites, whereas V5+ predominantly occupies a tetrahedral site. The paramagnetic 8g{V3+/4+}4 clusters are isolated by diamagnetic 2cV5+ cations. At temperatures below 500 °C the 8g{V3+/4+}4 clusters can be topotactically fine-tuned with varying V3+/V4+ ratios. Above 600 °C the tetragonal structure oxidizes to the cubic Sc2VO5+δ' fluorite phase-its disordered competitor. The investigation of the cation- and anion-ordered Sc-V-O phases, their formation, and thermal stability is important for the design of low-temperature solid state oxide ion conductors and vacancy structures.

authors

  • Vrublevskiy, Dmitry
  • Lussier, Joey A
  • Panchuk, Jenny R
  • Mauws, Cole
  • Beam, Jeremiah C
  • Wiebe, Christopher
  • Grosvenor, Andrew P
  • Bieringer, Mario

publication date

  • January 18, 2021