Photoluminescence in wide band gap corundum Mg4Ta2O9 single crystals
Li Liang, Zheng Yu-Lu, Hu Yu-Xin, Li Fang-Fei, Zhou Qiang †, Cui Tian
       

(a) Room-temperature transmittance and reflectance spectrum, with insert showing Mg4Ta2O9 crystal wafer, and (b) absorption spectrum with insert showing variation of (α hv)2 with photon energy (hv) of as-grown Mg4Ta2O9 crystal.