Influence of precipitant solution pH on the structural, morphological and upconversion luminescent properties of Lu2O3:2%Yb, 0.2%Tm nanopowders

► Lu2O3:2%Yb,0.2%Tm nanopowder was synthesized by co-precipitation method. ► Effect of precipitant pH on morphology and upconversion luminescence was studied. ► The sample obtained at pH=11 has the strongest upconversion emission. ► Blue, weak red and near infrared emission were observed under 980  nm excitation.