Highly condensed Eu<sup>2+</sup>-doped nitrodoberyllosilicates, <i>M</i>BeSi<sub>2</sub>N<sub>4</sub>:Eu<sup>2+</sup> (<i>M</i> = Ca, Sr): electronic structure and band gap studies
Bibliographic record
Abstract
Phosphor-converted light-emitting diodes (pc-LEDs) are a key technology in the reduction of global energy consumption. The understanding of the chemical and electronic properties of eligible substance classes is essential for applications of pc-LEDs. Here, the electronic structure, band gap, and band structure of highly condensed Eu2+-doped nitrodoberyllosilicates, MBeSi2N4:Eu2+ ( M = Ca, Sr) are studied using synchrotron-based soft X-ray absorption spectroscopy (XAS) and emission spectroscopy (XES) as well as density functional theory (DFT). The electronic band gaps for MBeSi2N4:Eu2+ are determined to be 4.20 ± 0.25 eV for M = Ca and 4.30 ± 0.25 eV for M = Sr using the combination of XAS and XES measurements. The measured band gap is in excellent agreement with our calculations (4.60 eV for M = Ca and 4.80 eV for M = Sr) using the Perdew–Burke–Ernzerhof variant of the generalized gradient functional, including a semilocal potential modified from that of Becke and Johnson. Based on the DFT calculations and the measurements, it is found that both compounds exhibit direct band gap transitions. The calculated partial density of states reveal that the N p-states dominate in the valence band for both materials, and the Ca d-states and Sr d-states dominate in the conduction band of CaBeSi2N4 and SrBeSi2N4, respectively. The observed electronic band gap is large enough, which will not interfere with the luminescent transition of 5 d → 4 f of Eu2+ emission. Thus, these two materials are promising candidates as host materials in pc-LEDs applications.
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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".