Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1590737 | Science and Technology of Advanced Materials | 2007 | 10 Pages |
Abstract
The crystal and electronic structures, as well as the luminescence properties of Sr2Al2âxSi1+xO7âxNx:Eu2+ are reported. First-principles calculations energetically confirm that the Al and Si atoms are in partial ordering in the 2a and 4e sites in Sr2Al2SiO7. In addition, the band structure calculation shows that Sr2Al2SiO7 has an indirect band gap with an energy gap of about 4.07Â eV, which is in good agreement with the experimental data (â¼5.3Â eV) obtained from the diffuse reflection spectrum. The crystal structure of Sr2Al2SiO7 can be modified by Si-N substitution for Al-O in the lattice with a maximum solubility of about x=0.6. The average bond length of EuSr-(O,N) slightly increases although the lattice parameters decrease with the incorporation of Si-N in Sr2Al2SiO7:Eu2+. Under excitation in the visible spectral region, Sr2Al2âxSi1+xO7âxNx:Eu2+ emits blue to yellow light with a broad emission band in the range of 480-570Â nm, varying with both the Eu concentration and the x value. The red shift of the emission band of Eu2+ is associated with an increase in the crystal-field splitting and the covalency, which arise from the incorporation of nitrogen as well as the energy transfer between the Eu ions at high Eu concentrations. Moreover, the Eu ions have a strong effect on both the concentration quenching and the thermal quenching in Sr2Al2âxSi1+xO7âxNx. The temperature dependence of photoluminescence indicates that Sr2Al2âxSi1+xO7âxNx:Eu2+ shows strong thermal quenching due to the dominant nonradiative process at room temperature.
Related Topics
Physical Sciences and Engineering
Materials Science
Materials Science (General)
Authors
Yuan Qiang Li, Naoto Hirosaki, Rong-Jun Xie, Mamoru Mitomo,