Achieving high dielectric energy-storage properties through a phase coexistence design and viscous polymer process in BNT-based ceramics

In the last few decades, dielectric capacitors have gotten a lot of attention because they can store more power and charge and discharge very quickly. But it has a low energy-storage density (W_rec), efficiency (η), and temperature stability. By adding Pb(Mg_1/3Nb_2/3)O₃ (PMN) and (Bi_0·1Sr_0.85)TiO₃ (BST) to a nonstoichiometric (Bi_0·51Na_0.5)TiO₃ (BNT) matrix, the goal is to change the phase transition properties and make the material more relaxor ferroelectric (RFE) by lowering the remnant polarization P_r and keeping the maximum polarization P_max. A viscous polymer process (VPP) is used to improve the electric breakdown strength, which is also a key part of being able to store energy. By working together, ceramics with the formula 0.79[0.85BNT-0.15PMN]-0.21BST (BP-0.21BST) are made. The phase structure has been changed from a rhombohedral phase to a rhombohedral-tetragonal coexisted phase. This is beneficial for RFE properties and gives a W_rec of 6.45 J/cm³ and a η of 90% at 400 kV/cm. Also, the energy-storage property is very temperature stable between 30 and 150 °C. These results show that process optimization and composition design can be used to improve the energy storage properties, and that the dielectric ceramic materials made can be used in high-powder pulse dielectric capacitors.