Promising method of complex oxide phases synthesis by using low hydrated hydroxides of niobium and tantalum (Nb,Ta)O-x(OH)(5-x).mH(2)O precursors of high reactivity and sorption ability was developed. Precursors, intermediate products of synthesis and target materials were studied by thermogravimetric analysis, infrared spectroscopy and X-ray diffraction. Sorption process of magnesium and lead cations by niobium low hydrated hydroxide from acetic solution allows obtaining PbMg1/3Nb2/3O3 complex perovskite without any secondary phase. (C) 2007 Elsevier Ltd. All rights reserved.