A co-precipitation reaction was used to prepare nanocrystal Gd6WO12:Eu3+ and Gd2WO6:Eu3+ red emitting phosphor powders with different Eu3+ doping levels. It is found that under the same preparation conditions, different doping level leads to different crystal structures; Gd6WO12-like with a tetragonal lattice structure tends to be synthesized at low doping level (10-40 mol%) yet Gd2WO6-like with a monoclinic lattice structure easily to grow at high doping level (60-80 mol%). The strong red emission of (5)Do-F-7(2) transitions at 620 nm was observed for all powders under either near ultraviolet or blue light excited and the most intense emission was obtained at the concentration of 40 mol%. This kind of powders might find their promising application to compensate the white LEDs for the lack of red light component and to improve rendering index. (c) 2012 Elsevier Ltd. All rights reserved.