Realizing high energy density and discharge energy density in high hardness Ba1.938Bi0.375Nb5O15-based glass ceramics

Abstract

The practical utility of glass-ceramics-based (GCs) energy storage materials is limited due to their low energy density. In this work, we synthesized the unleaded GCs containing two crystalline phases: Ba1.938Bi0.375Nb5O15 and BaNb2O6. An increase in crystallization time at a specific temperature initially leads to a decrease and then an increase in the dielectric permittivity (εr) and breakdown strength (BDS) due to changes in crystallinity. Specifically, at a crystallization temperature of 750 °C for 4 h, the BDS reaches approximately 1422 kV/cm, driven by a lower oxygen density, higher activation energy, and the formation of a fine-grained structure in the compact GCs. Numerical simulation was employed to uncover the underlying mechanism behind the enhanced BDS achieved through changing crystallization time. As a result of the enhanced BDS and polarization, this study achieved remarkable and comprehensive outcomes: a high efficiency (η) of 85.89%, a high energy density (Wrec) of 3.79 J/cm3, an ultrahigh discharge energy density (Wdis) of 3.26 J/cm3 and a high Vickers hardness (Hv) of 6.85 GPa. Meanwhile, this sample crystallized for 4 h demonstrates excellent thermal stability and frequency stability. These results show that these GCs could be highly competitive as lead-free materials for energy storage capacitors.