Cross-Relaxation and Upconversion Processes in Pr<sup>3+</sup> Singly Doped and Pr<sup>3+</sup>/Yb<sup>3+</sup> Codoped Nanocrystalline Gd<sub>3</sub>Ga<sub>5</sub>O<sub>12</sub>: The Sensitizer/Activator Relationship
Bibliographic record
Abstract
The room temperature luminescence properties of Pr 3+ -doped gadolinium gallium garnet (GGG:Pr 3+, Gd 3 Ga 5 O 12:Pr 3+ ) nanocrystals (0.1, 1, 5 and 10 mol %) were evaluated. Increasing the Pr 3+ concentration in the nanocrystals resulted in a decrease of the 3 P 0 emission to lower lying states via the [ 3 P 0, 3 H 4 ] → [ 3 H 6, 1 D 2 ] cross-relaxation (CR) process. Similarly, a decrease in the 1 D 2 emission was observed and was attributed to the [ 1 D 2, 3 H 4 ] → [ 1 G 4, 3 F 3,4 ] cross-relaxation mechanism. The increase in cross-relaxation efficiency on increasing the Pr 3+ concentration was attributed to the smaller average interionic distances between the dopant ions. Dominant blue/green emission due to the 3 P 0 → 3 H 4 and 3 P 0 → 3 H 6 transitions was observed after laser excitation at 457.9 nm for Pr 3+ /Yb 3+ codoped nanocrystalline GGG samples. The blue/green emission decreased as the sensitizer (Yb 3+ ) concentration increased in the GGG samples. The observed near-infrared (NIR) 2 F 5/2 → 2 F 7/2 emission from the Yb 3+ ion, upon 457.9 nm excitation, suggests the presence of an energy transfer process from the Pr 3+ ions to neighboring Yb 3+ ions and results in a decrease of room temperature visible emission with increasing ytterbium concentration. Upconversion emission was observed for 0.1 and 1 mol % single doped samples. The nanocrystalline GGG:Pr 3+,Yb 3+ codoped samples showed a notable increase in upconversion emission intensity relative to the singly doped samples excited upon 980 nm excitation radiation. Upconversion was observed to occur via an ET process for the single and codoped samples.
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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".