Ferroelectric properties and large electric field-induced strain of Eu3+-doped Na0.5Bi0.5TiO3–BaTiO3 lead-free ceramics

Eu³⁺-doped lead-free piezoelectric ceramics, 0.937Na_0.5Bi_0.5?xEu_xTiO₃-0.063BaTiO₃ (abbreviated as NBE_xT-BT, where x = 0, 0.003, 0.005, 0.01, 0.013, 0.015, 0.017, and 0.02), were synthesized using a conventional solid-state synthesis method. All the component samples were crystallized in a pure perovskite structure without a secondary phase. The introduction of Eu³⁺ caused the evident variation of the dielectric, ferroelectric and luminescence properties. The remanent polarization and coercive field of the pure NBT-BT are P_r ～29.24 μC/cm², E_c～39.33 kV/cm, respectively. The maximum of the remanent polarization P_r of ～38.02 μC/cm² at room temperature and the highest dielectric constant of 6899 with a frequency of 1 kHz were obtained for NBE_0.003T-BT. The maximum bipolar strain S_max of ～0.91% and the minimum of coercive field E_c ～18.45 kV/cm were achieved by the NBE_0.015T-BT, resulting from the formation of a double hysteresis loop. For all the components, Eu³⁺ doping stabilized the antiferroelectric phenomenon at high temperature. Furthermore, the polarized NBE_0.015T-BT had the strongest fluorescence luminescence intensity as well as a fluorescence lifetime reaching 785.98 μs.