Nanocrystalline La(1.5)Ln(0.5)Ti(2)O(7) (Ln=Pr, Gd, Er) solid solutions were prepared by a polymeric complex method. The samples were characterized by X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM), UV-vis diffuse reflectance spectra (DRS), energy dispersive Xray spectrum (EDS), thermogravimetric analyses (TGA) and differential thermal analyses (DTA). The photocatalytic activity of La(1.5)Ln(0.5)Ti(2)O(7) (Ln = Pr, Gd, Er) was evaluated by the photocatalytic degradation of methyl orange (MO). La1.5Gd0.5Ti2O7 showed the best photocatalytic activity and it was supposed that the half-filled electronic configuration of Gd3+ can promote charge transfer and enhance the photocatalytic activity. The difference in the photocatalytic activity observed for La(1.5)Ln(0.5)Ti(2)O(7) (Ln = La, Pr, Gd, Er) can be related to the different Ln 4f shell. (c) 2006 Elsevier B.V. All rights reserved.