Regulating ferroelectric polarization and dielectric properties of BT-based lead-free ceramics

The ternary system of BaTiO3 (BT) -based lead-free ceramics ((1-x)BaTiO3-x(0.94 Sr0.7Bi0.2TiO3-0.06BiMg0.5Ti0.5O3) are investigated on their structural, dielectric and ferroelectric properties. The structural evolution is identified from the tetragonal phase (P4mm) to the pseudocubic phase with increasing the dopant concentration x. The gradually diffusive dielectric peak and highly dispersive relaxor behaviors are recognized, indicating the transformation from ferroelectric to relaxor state. Meanwhile, the ceramics are characterized by the slim polarization hysteresis loops associated with polar nano-sized cluster formation. Complex impedance spectroscopy reveals the electrical inhomogeneities with enhanced boundary effect caused by the excessive addition, leading to the abnormally degraded electric breakdown strength. Combined with the X-ray photoelectron spectroscopy, the oxygen vacancy hopping mechanism is proposed for the high dopant concentration, contributing to the diffuse dielectric response. As a result, optimized energy-storage density and efficiency are simultaneously obtained at a relatively low electric field. All these features demonstrate an effective route in the composition modulation of BT-based dielectric capacitor ceramics that not only the formation of polar nano regions but also the electrical homogeneities can greatly influence the comprehensive dielectric performance. •The phase structure and dielectric performances of BaTiO3-based ternary system are investigated through SBMT substitution.•The transformation from ferroelectric to relaxor state is identified in BT-SBMT ceramics.•An outstanding energy storage density with high efficiency is obtained at relatively low electric fields.•The electrical inhomogeneities lead to the diffuse dielectric behavior and degraded electric breakdown strength.