Ab-initio study of paramagnetic defects in Mn and Cr doped transparent polycrystalline Al2O3 ceramics
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Bibliographic record
Abstract
Birefringence is a major source of difficulty in sintering of transparent polycrystalline alumina ceramics, especially as the grain size exceeds a few hundred nanometers, which ultimately leads to complete opacity, mainly due to scattering of light. Recent studies have made it clear that by application of a strong magnetic field, alumina grains can be aligned along a particular crystallographic orientation, which minimizes scattering due to birefringence, and enhances transparency. Defects that cause spin delocalization are known to induce a paramagnetic behavior in alumina ceramics. Therefore, such defects have become a focal point of research for magnetic field assisted sintering of transparent polycrystalline alumina, in order to reduce the necessary magnetic field strength during production process. In light of recent studies on paramagnetic potentials of transition metal doped alumina, we have applied Spin Polarized Density Functional Theory (SP-DFT) calculations on manganese and chromium doped and co-doped alumina to calculate the magnetic moments, density of states and defect formation energies, which should be expected from this system of dopants, along with their interactions with oxygen vacancies. The results clearly indicate that formation of a point defect comprised of chromium and manganese positioned substitutionally at adjacent aluminum sites, in vicinity of an oxygen vacancy can induce a magnetic moment equivalent to 5 Bohr magnetons (μβ), outperforming previously reported defects. Based on this study we find it likely that chromium and manganese co-doping in alumina can further reduce the required magnetic field strength for production of transparent polycrystalline alumina.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.000 | 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 it