Photocurrents, pyroelectric currents and photovoltaic currents in ferroelectric Sr 0.5Ba 0.5Nb 2O 6 (SBN50) were investigated. These quantities were measured as a function of temperature. By doping the rare-earth ion Pr 3+ into the sample, SBN changed to a relaxor ferroelectric with a diffuse phase transition. The relation between the diffuse phase transition and the photoexcited phenomena were explained in terms of the role of the dopant ions