By the methods of physicochemical analysis (DTA, XRD, MSA), as well as the density and microhardness measurements the effect of terbium content on the physicochemical properties of solid solution (Bi₂Sb₅Se₃Te₆J₃) n-type has been studied and microchart built. It has been established that in the system ((Bi₂Sb₅Se₃Te₆J₃)_1-x(Tb)_x at room temperature on the basis of (Bi₂Sb₅Se₃Te₆J₃) 5 mol. % Tb dissolves. The system forms an eutectic composition of which meets 15 at. % Tb, and melting point is 500⁰C.