研究目的
Investigating the formation of color centers in magnesium aluminate spinel through X-ray and electron irradiations, determining the threshold displacement energy for oxygen atoms, and analyzing thermal recovery processes.
研究成果
The research confirms a high threshold displacement energy of 190 ± 10 eV for oxygen atoms in magnesium aluminate spinel, higher than simulation predictions. Color centers form through elastic collisions, with F0 and F+ centers reaching equipartition at high fluences. Thermal recovery shows non-zero asymptotic behavior due to charge exchange equilibria. Stokes shifts are derived, providing insights into electron-phonon interactions. The findings have implications for radiation damage studies in materials science.
研究不足
The study is limited to specific irradiation conditions (energies and fluences) and temperatures; discrepancies with molecular dynamics simulations are noted, and the mechanisms for high threshold displacement energy and charge exchange processes require further investigation. The analysis assumes certain models (e.g., Gaussian fitting) that may not capture all complexities.
1：Experimental Design and Method Selection:
The study involved irradiating magnesium aluminate spinel samples with X-rays (Cu Kα radiation) and electrons (1.0, 1.4, and 2.5 MeV energies) at room temperature to induce color-center formation. UV-visible absorption spectroscopy was used to monitor the effects, with spectra recorded at various temperatures and fluences. The methodology included fitting absorption bands with Gaussian profiles and analyzing production rates and thermal recovery.
2：0, 4, and 5 MeV energies) at room temperature to induce color-center formation. UV-visible absorption spectroscopy was used to monitor the effects, with spectra recorded at various temperatures and fluences. The methodology included fitting absorption bands with Gaussian profiles and analyzing production rates and thermal recovery.
Sample Selection and Data Sources:
2. Sample Selection and Data Sources: Single crystal plates of magnesium aluminate spinel with (100) orientation and 500 μm thickness were supplied by MTI corporation. Samples were polished for optical measurements. Data were collected from irradiation experiments and subsequent spectroscopic analyses.
3：List of Experimental Equipment and Materials:
Equipment included an X-ray diffractometer for X-ray irradiation, the SIRIUS accelerator for electron irradiations, a Perkin-Elmer Lambda-1050 spectrometer for UV-visible absorption measurements, a helium-cryostat for low-temperature measurements, and a TS1500 micro-thermometric stage for high-temperature annealing. Materials included the spinel samples and helium gas for beam conditions.
4：Experimental Procedures and Operational Workflow:
Irradiations were performed with specified fluences and energies. Absorption spectra were recorded offline at RT and low temperatures, and in situ during annealing. Spectra were analyzed by subtracting reference spectra and fitting with Gaussian components. Annealing involved isochronal and isothermal steps with temperature control.
5：Data Analysis Methods:
Data analysis included least-square fitting of absorption bands, computation of displacement cross sections using codes like ESTAR and SMOTT/POLY, and kinetic analysis of annealing data using exponential decay models and rate equations for charge exchange processes.
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