Аннотация:Influence of complex CaCl2/KCl additive with low melting temperature ~870 K on structure, dielectric and polar properties of ceramic solid solutions on the base of composition from Morphotropic Phase Boundary in the system (1-x)BiScO3 - xPbTiO3 (x=0.635, 0.64, 0.645) was studied. Using initial compositions prepared from nitrates solutions dense single phase ceramic samples doped by the additives in amounts up to 5 w.% were obtained at 1320 K.Variations in relative content of rhombohedral and tetragonal phases, changes of crystal structure parameters, and polar properties were observed depending on both x value and amount of additive. Temperature of the 1st order ferroelelctric phase transitions decreased from ~700 K to 630-650 K in the doped samples due to the introduction of Ca2+/K+ ions into A sites of perovskite lattice.