Synthesis, Rietveld refinement of crystal structure, electron diffraction, and electrical transport properties of Ba<sub>2</sub>(Ca<sub>1–<i>x</i>–<i>y</i></sub>Fe<i><sub>x</sub></i>Nb<i><sub>y</sub></i>)(Nb<sub>1–<i>z</i></sub>Fe<i><sub>z</sub></i>)O<sub>6–δ</sub> double perovskites
Bibliographic record
Abstract
We report the synthesis, crystal structure, and electrochemical properties of new Fe-doped Ba2(Ca1–x–yFexNby)(Nb1–zFez)O6–δ (Fe–BCN). The Fe–BCN was synthesized by a solid-state method in air using corresponding metal oxides and salts at elevated temperature. All of the observed powder X-ray diffraction (PXRD) peaks of the investigated Fe–BCN were indexed as cubic Fm-3m (space group No. 225) double perovskite-type structure with cell constants a ∼ 8.4 Å and is consistent with selected area electron diffraction (SAED). Rietveld analysis suggested the distribution of Fe was at both 4a and 4b sites, supported the proposed chemical formula Ba2(Ca1–x–yFexNby)(Nb1–zFez)O6–δ. This was further verified by bond valence sum (BVS) analysis of the cations. The Fe–BCN showed superior chemical stability in pure CO2 and boiling H2O confirmed by PXRD and FTIR. The electrical conductivity was determined by AC impedance spectroscopy. Among the samples investigated, Ba2(Ca0.79Fe0.21)(Nb0.71Fe0.29)O6–δ showed the highest total (bulk + grain-boundary) conductivity of 1.1 × 10−2 S cm–1 in humidified (3%) N2 at 600 °C with activation energy of 0.43 eV in the temperature range 200–800 °C.
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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".