采用球磨法制备了不同浓度Cr_2O_3掺杂的Al_2O_3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-Al_2O_3相外,其余样品相均为纯α-Al_2O_3。样品晶格常数随着Cr~（3＋）离子浓度的增加而增加。采用波长为579 nm的激发光源对佯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Cr~（3＋）离子中电子由2A能级到~4A_2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Cr~（3＋）未能完全替代Al_2O_3中的Al~（3＋）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。
Cr~（3＋）：Al_2O_3 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 theα-Al_2O_3 structure,except that there are some low-intensity peaks ofγ-Al_2O_3 appearing in the Cr（1.6%）- doped sample.The samples＇ lattice constants increase with the increase of the doping of Cr~（3＋） 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 Cr~（3＋） ions＇ electronics from 2A to ~4A_2 and the 0.3%Cr doped sample shows the greatest fluorescence emission intensity.When the doped concentration was greater than 0.3%,too many Cr~（3＋） 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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