Improvement of dielectric and energy storage properties in SrTiO3-based lead-free ceramics

The (1-x)SrTiO3-xBi0.5(Na0.82K0.18)0.5Ti0.96Zr0.02Sn0.02O3 ((1-x)ST-xBNKTZS) lead-free ceramics with x = 0-0.5 were designed and fabricated using the conventional solid-state sintering method. Their phase structure, microstructure, dielectric, ferroelectric and energy storage properties were systematically investigated. The dielectric constant of (1-x)ST-xBNKTZS ceramics increases gradually and reaches the maximum value (∼2650) with x = 0.5 at 1 kHz, which is 8.83 times as large as that of pure ST (∼300). All the samples show slim polarization-electric field (P-E) hysteresis loops and the maximum polarization (Pmax) can be improved to 20.65 μC/cm2 with x = 0.5 at 100 kV/cm, which is 6.20 times as large as that of pure ST (3.33 μC/cm2). The sample with x = 0.4 exhibits a high energy storage density (1.45 J/cm3) and a high energy storage efficiency (86%) simultaneously. These results indicate that the (1-x)ST-xBNKTZS ceramics may be promising lead-free materials for high energy storage capacitors.