Investigation of amorphous to crystalline phase transition of sodium titanate by X-ray absorption spectroscopy and scanning transmission X-ray microscopy
Bibliographic record
Abstract
Nanostructured sodium titanate has great potential for various applications such as sodium-ion batteries, photocatalysts, and waste treatment. Understanding the phase-transition mechanism in sodium titanate after annealing is fundamentally important to tune the structure, morphology, and property for targeted applications. In this work, we adopted amorphous sodium titanate grown on carbon nanotubes by an atomic layer deposition technique as a reference and used X-ray absorption spectroscopy (XAS) and scanning transmission X-ray microscopy (STXM), as well as a high-temperature in situ X-ray diffraction (XRD) technique, to elucidate the phase-transition mechanism of sodium titanate from amorphous to crystalline upon annealing from 25 °C to 900 °C. XAS and XRD analysis disclosed that anatase TiO2 first formed in the matrix of amorphous sodium titanate at 500 °C and then recrystallized into Na0.23TiO2 at 700 °C and 900 °C. XAS studies also revealed that the Ti atoms in sodium titanate were oxidized during the annealing process and reached an oxidation state about 3.8+ for Na0.23TiO2. The elevated annealing temperature increased the coordination number of Ti atoms and the crystallinity of sodium titanate. STXM chemical map provided spatial information and visualized evidence on the phase transition among amorphous sodium titanate, anatase TiO2, and Na0.23TiO2 in the samples annealed at intermediate temperatures (500 °C and 700 °C). This work provides a comprehensive understanding on the evolution of sodium titanate, in terms of crystal structure, electronic structure, chemical environment, and morphology, under different post annealing conditions.
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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".