Relaxor ferroelectrics Pb(Sc1/2Nb1/2)O-3 (PSN) attracted intensive attention due to its unique properties such as ordering-disordering transition of B/B' cations. In this work, the effect of pH value on the PSN powders by the precipitation method was systematically investigated. The experiments show that the formation of perovskite PSN was strongly related to the pH condition, which impacts the chemical stoichiometry of the precipitates and grain morphologies of the PSN powders: at low pH condition, the perovskite PSN was accompanied with the pyrochlore phase due to the deficiency of Pb; however, high pH value resulted in the large size of the powders due to the strong agglomeration effect of OH- wrapping, even though the pure perovskite PSN powders was obtained. The PSN powders precipitated at a mild pH of 8.1 achieved a pure perovskite PSN powders with chemical stoichiometry and grain size of 400 run. Besides, the dielectric measurements of PSN ceramics prepared by precipitation method show the typical relaxor ferroelectrics characteristics, and a more diffusive phase transition than that for PSN ceramics fabricated by conventional solid-state reaction method. (C) 2007 Elsevier B.V. All rights reserved.