Synthesis and Luminescence Study of Mn-doped Nanosized Al2O3

Mn³+-doped Al2O3was obtained by combustion method. It was found that the resulting powder, with particle sizes of 10–70 nm, consists of a mixture of transition aluminas $(\delta^{*}, \delta,\ \theta)$, among which $\delta^{*}$ -polymorph is dominant. The presence of Mn³+ ions results in a wide absorption band in the 400–620 nm region, but no emission of these ions was observed, probably due to a strong Jahn-Teller effect. It is shown that a part of Mn impurity ions exists in the oxidation state +2 and occupies tetrahedral positions in the $\delta^{\star}-\mathrm{A}1_{2}\mathrm{O}_{3}$, causing a broad emission band with a maximum at 520 nm.