The present paper deals with substrate heterostructure effects on the microstructure and dielectric properties of Sm, Er, and La doped lead titanate (PT) thin films. The substrate heterostructures chosen include Si/(La0.8Sr0.2)MnO3 (LSMO), Y-stabilized zirconia (YSZ)/LSMO and Si/Pt. Both LSMO and PT thin films were processed via chemical solution deposition. The results are compared to those of Sm and Er doped lead-zirconate-titanate (PZT). It is shown that the dielectric properties, and particularly the ferroelectric-to-paraelectric transition temperature of PT, are strongly affected by the substrate heterostructure. In comparison to PT on platinized Si, the transition temperature is shifted by more than 100°C towards lower values in the case of Er and Sm doped PT on LSMO, while those of La doped PT and PZT are not affected at all. X-ray photoelectron spectroscopy investigations show a substantial interdiffusion between LSMO and PT. Particularly the diffusion of La towards the ferroelectric film and that of Pb towards LSMO are made responsible for the change in the dielectric properties. In the case of PZT we stipulate the formation of a stable pyrochlore diffusion barrier layer.