Ceramic solid solutions on the base of composition from morphotropic phase boundary 0.36BiScO3-0.64PbTiO3 modified by the powdered Bi4Ti3O12 and Bi0.75Sr0.25O1.36 single crystals additives and by the low-melting LiF additive in amounts 5, 10, and 1 wt.%, respectively, have been prepared by the solid-state reactions method. The structure, microstructure, and dielectric properties of the ceramics have been studied. The influence of the additives on the morphology of ceramics, temperature of phase transitions, and effect of dielectric relaxation has been proved.