Dielectric, piezoelectric, and ferroelectric properties of Al ₂O₃ and MnO₂ modified PbSnO₃- PbTiO₃-Pb(Mg_1/3Nb_2/3)O₃ ternary ceramics

The PbSnO₃-PbTiO₃-Pb(Mg_1/3Nb _2/3)O₃ (PST-PMN) ternary system with morphotropic phase-boundary (MPB) compositions were fabricated using a two-step columbite precursor method. The effects of Al₂O₃ and MnO₂ addition on the dielectric, piezoelectric, and ferroelectric properties of PST-PMN were investigated. MnO₂ acted as an acceptor dopant and induced a "hardening" effect in PST-PMN, with decreased piezoelectric coefficients d₃₃ and increased mechanical quality factors Q _m, while the addition of Al₂O₃ led to the significant decrease of piezoelectric properties, attributed to the second phase. Of particular interest is the fact that the Mn-doped PST-PMN exhibited excellent properties when the doping level was in the range of 0.2-0.5 wt%, with piezoelectric d₃₃, planar electromechanical coupling k_p, dielectric permittivity Ïμ_r, Q_m, remnant polarization P_r and coercive field E_C being on the order of ∼510 pC N^-1, ∼57%, 3120-3500, 530-600, 27-30 μC cm ^-2, and ∼8 kV cm^-1, respectively, showing advantages over commercial PZT4-type ceramics, which are promising for high-power electromechanical applications.