Influence of La3+ and Fe3+ co-doping to nano-TiO2 prepared by graded calcination

► La3+ and Fe3+ co-doped TiO2 sample was prepared by a new process. ► The gelatinizing time is obviously shortened. ► The grain size of co-doped TiO2 sample is decreased. ► The photocatalytic activity of co-doped TiO2 under visible light is improved.