(1-x)BaTiO3-xBi(Mg1/2Ti1/2)O-3 [(1-x) BT-xBMT] polycrystalline ceramics were obtained via solid-state processing techniques. The solubility limit for (1-x) BT-xBMT was determined to be about x = 0.07. A systematic structural change from the ferroelectric tetragonal phase to pseudocubic phase was observed at about x >= 0.05 at room temperature. Dielectric measurements revealed a gradual change from normal ferroelectric of pure BaTiO3 to highly dispersive relaxor-like characteristics in the solid solution with 30-60 mol% Bi(Mg1/2Ti1/2)O-3, showing low-temperature coefficients of capacitance over a wide temperature range. The properties of Nb2O5-doped 0.85BT-0.15BMT ceramics were investigated to better understand the formation mechanism of core-shell structure, for further improving the temperature stability of the dielectric behavior.