We have synthesized high-purity Yb3+-doped Lu2O3 powder by the coprecipitation method. We have demonstrated that the recrystallization of the metal nitrates greatly improve the chemical purity of the resulting oxides. From thermogravimetry and differential thermal analysis study, we have calculated the approximate formula of the oxinitrate precipitate precursor as Lu1.8Yb0.2(OH)(5.44)(NO3)(0.56).0.58H(2)O. Fine and soft agglomerate powders were obtained after calcinations. We have shown that the powder is mainly in the form of polycrystalline soft agglomerates composed with 15-20 nm size crystals. The resulting ceramic showed higher transparency (close to theoretical limit) compared with the ones fabricated with commercial powders.