The phase formation kinetics and phase relations in the BaCO 3-PbO-Nb2O5 system are studied. Barium lead niobates are prepared by solid-state reactions, and the composition ranges of solid solutions with different structures are determined. All of the materials are examined by x-ray diffraction, and their stability in acid media is assessed. The electrical conductivity of the Pb-containing niobates is measured. The results are used to analyze property-structure-composition relations. Based on the phase-equilibrium data and the chemical stability and electrical properties of the niobates, the structure types and compositions of niobates are identified which are the most attractive for producing ion-selective materials.