Bi(Mg2/3Nb1/3)O-3 was systematically substituted (up to 30 mol%) into Pb(Mg1/3Nb2/3)O-3-PbTiO3 and resultant changes in the phase formation, crystallographic aspects as well as dielectric properties of the ceramic samples were investigated. Columbite and rutile solid solutions were mostly detected in the B-site precursor compositions, whereas only a monophasic perovskite structure was identified after the addition of PbO and Bi2O3. Frequency-dependent dielectric relaxation behavior was observed in all of the compositions investigated. The maximum dielectric constant values decreased substantially with increasing substituent fractions of Bi. By contrast, the dielectric maximum temperatures changed in somewhat complicated ways in that the increase became comparatively insensitive to the PbTiO3 concentration with increasing levels of Bi substitution. (C) 2006 Elsevier Ltd. All rights reserved.