  Results presented in this article demonstrate importance of taking into
account such a phenomenon as the solid solution decomposition at the boundaries
separating coexisting phases in lead-zirconate-titanate-based solid solutions
with compositions belonging to the morphotropic boundary region of the
"temperature-composition" phase diagram. It is shown that in the local
decomposition of solid solutions in the vicinity of the boundaries separating
the tetragonal and rhombohedral phases in lead-zirconate-titanate-based solid
solutions lead to the changes of the chemical composition of the solid
solutions and to the formation of segregates. It is also shown that the proper
thermoelectric treatment of samples containing these segregates can give
substantially higher values of piezoelectric parameters in the
lead-zirconate-titanate-based compounds.
