采用球磨法制备了不同浓度Cr2O3掺杂的Al2O3粉体, 并在700℃、1200℃空气中退火2 h。1200℃退火后样品, 除掺杂浓度为1.6%的样品中出现少量γ--Al2O3相外, 其余样品相均为纯α--Al2O3。样品晶格常数随着Cr3+离子浓度的增加而增加。采用波长为579 nm的激发光源对样品进行荧光光谱检测发现所有样品在469--492 nm波段, 均出现F+心所引起的缺陷发光峰。1200℃退火的所有样品都出现一个由Cr3+离子中电子由2A能级到4A2能级跃迁引起的在694 nm的强烈发光带, 掺杂浓度为0.3%时发光强度最高。当掺杂浓度高于0.3%时, 样品中Cr3+未能完全替代Al2O3中的Al3+离子, 出现耦合, 产生浓度猝灭现象, 导致该波长发光强度减弱。对比而言, 700℃退火样品仅掺杂浓度为0.3%时出现694 nm的发光, 且强度较低。
Cr3+ : Al2O3 nano-powders were prepared by ball milling method and annealed at 700℃ or 1200℃ for 2 h in the air. The samples annealed at 1200℃ are of single phase with the α–Al2O3 structure, except that there are some low-intensity peaks of γ–Al2O3 appearing in the Cr(1.6%)–doped sample. The samples' lattice constants increase with the increase of the doping of Cr3+ ions. Using the excitation source with a wavelength of 579 nm, the photoluminescence (PL) spectra of all the samples shows a strong emission band between 469 nm and 492 nm, which is ascribed to the absorption of F+ color center. The samples annealed at 1200℃ show a strong emission band at 694 nm caused by the transition of Cr3+ ions’ electronics from 2A to 4A2 and the 0.3% Cr doped sample shows the greatest fluorescence emission intensity. When the doped concentration was greater than 0.3%, too many Cr3+ ions can couple and lead to concentration quenching. In contrast, for the samples annealed at 700 !, only the 0.3% Cr doped sample exhibits a low–intensity emission peak at 694 nm.
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