Small amounts of lanthanum and potassium dopants could modify the microstructure and dielectric properties of 0.90Bi(0.5)Na(0.5)TiO(3)-0.10PbTiO(3) and 0.88Bi(0.5)Na(0.5)TiO(3)-0.12PbTiO(3) solid solutions. La lowered both phase transition temperatures of ferroelectric to antiferroelectric and antiferroelectric to paraelectric. It also decreased the maximum value of relative dielectric permittivity of the composition. In contrast, K shifted the first phase transition to the lower temperature but insignificantly affected the Curie temperature and raised the maximum dielectric permittivity. Furthermore, K influenced the microstructure in the way to enhance the long grains of this solid solution but La inhibited this effect.