Dielectric behavior of Mn-doped morphotropic phase boundary composition in the Pb(Zn_1/3Nb_2/3)O₃-BaTiO₃- PbTiO₃ system

The dielectric behavior of manganese-doped morphotropic phase boundary (MPB) composition in the Pb(Zn_1/3Nb_2/3)O₃- BaTiO₃-PbTiO₃ (PZN-BT-PT) system is described in this paper. Materials with perovskite structure were fabricated using the precursor approach. Addition of Mn stabilized the rhombohedral phase against the tetragonal one, moving the MPB territory toward the PbTiO₃-rich side. Both the dielectric permittivity maximum (ε′_m) and phase transition temperature (T_max) were reduced by increasing Mn²⁺ content. Frequency-dispersion characteristics of T_max were weakened while the frequency spectrum of the dielectric permittivity (ε′) was broadened, reflecting different underlying mechanisms. The broadness of paraelectric to ferroelectric phase transition was significantly enhanced by Mn-doping. This was associated with progressive increase in the degree of chemical heterogeneity on B-site cations. The observed proximity of the non-Curie-Weiss region to T_max as well as shrinkage of this region for doped compositions suggest increased stability of the ferroelectric phase.