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Lead-free ferroelectric ceramics (1-x) BaTiO3–xBi(Mg1/2Ti1/2)O3 (x = 0.0–0.07) were synthesized by conventional solid state reaction method and the correlation of structure, dielectric, ferroelectric and impedance properties were investigated. It was found that Tm and εm showed decreasing trend with the increase of BMT content. The high-temperature dielectric relaxation behaviour was observed in all the samples. The activation energy calculated from impedance (Ea) and conductivity (Econd), which revealed that the relaxation behaviours were linked with the migration of OVs. The values of Ea were almost equivalent to Econd. It was concluded that the short-range hopping of oxygen vacancy contributed to the dielectric relaxation and long-distance movement of doubly ionized oxygen vacancies contributed to the conduction. On the other hand, with increasing BMT contents, it was found that P-E loops became slimmer and slimmer, which indicated the increase of relaxor behaviour. The temperature dependence of P-E loops for 0.98BT–0.02BMT ceramic clearly showed the transition process from ferroelectric to relaxed ferroelectrics. Keywords: BT–BMT ceramic, Dielectric, Ferroelectric, Impedance, Oxygen vacancies