Er3+(/Yb3+)-doped Li3NbO4 powder were prepared by thermally sintering mixtures of Er2O3 (0.5, 1.0 mol%). Yb2O3 (0 0.5, 1.0 rnol%), Li2CO3 (48-49 mol%) and Nb2O5 (50 mol%) at 1125, 1150 and 1450 degrees C over the durations of 8-22 h. The crystalline phases contained in theme samples were determined by using, X-ray diffraction and discussed in comparison with a vapor-transport-equilibration-treated (VTE-treated) Er(2.0 mol%):LiNbO3 single crystal and ErNbO4 powder previously reported. The results show that the X-ray patterns of the rare-earth-doped samples reveal little difference each other, but large differences with those of the VTE crystal and ErNbO4 powder. The doped rare-earth ions Er3+ (and Yb3+) present in the powder as the ErNbO4 (and YbNbO4) phase(s). The possibility that the highly Er-doped LiNbO3 crystal contains Li3NbO4 precipitates is small. Optical absorption and emission studies show that the only Er-doped Li,NbO4 powder shows similar absorption and emission characteristics with the pure ErNbO4. The codopant Yb3+ ion enhances the 980-nm-upconversion emissions of Er3+ ions, results in remarkable spectral alterations at 0 98 mu m region, and causes the alterations of relative absorbance and relative emission intensity of individual peaks or bands at 1.5 [mu m region. On the other hand, the Yb-codoping hardly affects the Er3+ energy structure and the lifetime of Er3+ ion at 1.5 mu m. The measured lifetimes at 1.5 mu m of Er3+ ions in the singly Er3+- and doubly Er3+/Yb3+-doped mixtures have a nearly same value of similar to 1.5 ms. For the pure ErNbO4 powder, the lifetime is prolonged to similar to 2 ms perhaps due to radiation trapping effect.