Influence of niobium doping on phase composition and defect-mediated photoluminescence properties of Eu3+-doped TiO2 nanopowders synthesized in Ar/O2 thermal plasma

► Nb5+:Eu3+-codoped TiO2 nanopowders were synthesized by Ar/O2 thermal plasma. ► The resultant powders have mixture polymorphs of anatase as a major phase and rutile. ► Rutile formation was promoted by Eu3+ doping but was suppressed by Nb5+ addition. ► The resultant powders consist of facet-shaped particles and nearly spherical crystals. ► The intensity ratio of PL from 5D0 → 7F2 and 5D0 → 7F1 was weaken with Nb5+ content.