Understanding the Interplay of Vacancy, Cation, and Charge Ordering in the Tunable Sc<sub>2</sub>VO<sub>5+δ</sub> Defect Fluorite System
Bibliographic record
Abstract
We report the synthesis, structure, and redox behavior of the cation-ordered tetragonal Sc 2 VO 5+δ defect fluorite superstructure previously thought to be the oxygen precise A 3+ 2 B 4+ O 5 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 Sc 2 VO 5+δ and the disordered cubic Sc 2 VO 5+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 Sc 2 VO 5+δ phase with δ = −0.15(2) for as-synthesized samples reveals vanadium charge ordering. V 3+ and V 4+ cations occupy octahedral sites, whereas V 5+ predominantly occupies a tetrahedral site. The paramagnetic 8 g {V 3+/4+ } 4 clusters are isolated by diamagnetic 2 c V 5+ cations. At temperatures below 500 °C the 8 g {V 3+/4+ } 4 clusters can be topotactically fine-tuned with varying V 3+ /V 4+ ratios. Above 600 °C the tetragonal structure oxidizes to the cubic Sc 2 VO 5+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.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".