Symmetry changes during relaxation process and pulse discharge performance of the BaTiO₃-Bi(Mg_1/2Ti_1/2)O₃ ceramic

Lead free relaxor ferroelectrics have attracted continuing interest due to their outstanding and eco-friendly properties. In this paper, dielectric relaxation behavior of the 0.6BaTiO₃-0.4Bi(Mg_1/2Ti_1/2)O₃ ceramic (BT-40BMT), which is a typical lead free relaxor ferroelectric, is theoretically and experimentally investigated. At first, the observed dielectric relaxation was quantitatively characterized by a statistical model, indicating that the minority co-related polar nano regions (PNRs) dominate the total polarization. Kinetics of the PNRs were subsequently studied by micro-Raman measurements performed at various temperatures. Here, the relaxation of written domains formed by the piezoresponse force microscopy (PFM) tip-bias induced electric field was also studied, which describes the polarization retention performance of BT-40BMT. The absence of ferroelectric signal contribution in local switching was also confirmed by the contact mode Kelvin PFM technique, indicating the lack of local ferroelectricity. Moreover, the temperature insensitive energy storage property from 293 K to 443 K was obtained. High voltage pulsed discharge behavior was also investigated by using the pulsed current. A power density of 7.9 × 10⁸ W/kg is obtained under a pulsed voltage of 50 kV. Combined with the fast discharge time, the 0.6BaTiO₃-0.4Bi(Mg_1/2Ti_1/2)O₃ ceramic is considered as a candidate material for high voltage pulse power applications.