The Influence of Mg Doping in α-Al₂O₃ Crystals Investigated with First-Principles Calculations and Experiment

Area of Science:

• Materials Science
• Solid State Physics
• Computational Materials Science

Background:

• Aluminum oxide (α-Al2O3) is a widely used ceramic material with tunable optical and radiation properties.
• Doping α-Al2O3 with magnesium (Mg) can alter its defect structure and performance.
• Understanding Mg doping mechanisms is crucial for advanced material applications.

Purpose of the Study:

• To investigate the influence of Mg doping on the electronic and optical properties of α-Al2O3 crystals.
• To elucidate the formation mechanisms of Mg-related defects, including oxygen vacancies.
• To compare the optical and radiation performance of Mg-doped α-Al2O3 with Mg-rich spinel structures.

Main Methods:

• First-principles calculations (density of states, formation energies).
• Modeling of Mg substitutional doping (MgAl) and oxygen vacancies (VO).
• Experimental characterization including absorption spectra and thermoluminescence measurements.

Main Results:

• Formation energy calculations favored the MgAlVO model, indicating Mg substitution with oxygen vacancies is the most probable defect structure.
• Mg doping and oxygen vacancies introduce new energy levels within the bandgap, creating color centers.
• Calculated absorption spectra matched experimental results, validating theoretical predictions.
• Alumina-magnesium (Al-Mg) spinel exhibited significantly stronger thermoluminescence than Mg-doped α-Al2O3.

Conclusions:

• Mg2+ substitutional doping in α-Al2O3, particularly with co-existing oxygen vacancies, significantly influences its optical properties.
• The formation of locally Mg-rich spinel phases impacts the overall optical and radiation performance of Mg-doped alumina.
• Computational and experimental findings provide a comprehensive understanding of Mg doping effects in α-Al2O3.