Effect of synthesis method and reaction conditions on the long-range and local structure of RE<sub>2</sub>Ti<sub>2</sub>O<sub>7</sub> pyrochlore-type oxides
Bibliographic record
Abstract
Current plans for managing high-level nuclear waste may involve sequestration in borosilicate glass and potential disposal in geological repositories. However, there is considerable interest in using ceramic oxides, such as pyrochlores, as alternative nuclear waste forms due to the high chemical durability and waste loading capabilities of these materials. The ceramic method is often used to synthesize RE2Ti2O7 pyrochlore-type oxides and requires the use of high temperatures and long reactions times, making this process less economically feasible for large-scale production. Solution-based synthetic routes, such as co-precipitation and sol–gel methods, have been shown to require much lower reaction temperatures by reducing diffusion distances between reactants. This work studied the effect of using these synthetic methods to synthesize RE2Ti2O7 (RE = Gd, Yb). The resistance to radiation induced damage of these materials was also investigated. Phase transitions in RE2Ti2O7 were investigated using powder X-ray diffraction, X-ray absorption near-edge spectroscopy (XANES), and extended X-ray absorption fine structure. Changes to the structure of ion-implanted materials were investigated using glancing-angle (GA-)XANES. This study demonstrated that solution-based methods used to mix the reactants can allow for the formation of Yb2Ti2O7 adopting primarily the pyrochlore-type structure when annealed at temperatures as low as 1000 °C while Gd2Ti2O7 adopting the pyrochlore-type structure could be formed using annealing temperatures as low as 800 °C. It was also observed that changing the synthetic method, annealing temperature, annealing time, and having only the pyrochlore structure present or a mixture the pyrochlore- and defect-fluorite type structures did not affect the resistance to radiation induced structural damage of Yb2Ti2O7 or Gd2Ti2O7.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 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) | 0.002 | 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".