Grain refinement and polarization enhancement synergistically triggered NBT-based piezoceramics enabling sustainable high power generation

Lead-free piezoelectric energy harvesters (PEHs) with long-term stable power generation capability is an important solution for realizing reliable self-power supply of microelectronic devices such as wireless sensors. As the core of PEHs, piezoceramics with practical value require not only high figure of merit (FOM) to achieve high power generation, but also strong fracture toughness (KIC) to prevent the fracture failure caused by long-term cyclic vibration, which poses a challenge to the material design. To address these concerns, K0.5Bi0.5TiO3 was rationally introduced into Na0.5Bi0.5TiO3 matrix, and the synergistic effect of grain refinement and polarization enhancement was realized through composition design and grain size regulation to obtain excellent performance with KIC of 1.57 MPa·m1/2 and FOM of 1.94 × 10−12 m2/N. The cantilever beam-type PEH with the optimal sample achieved a high output power density of 395.5 μw/cm3, in particular, under different acceleration conditions (1g-3g), after 106 cycles, the PEH can still maintain a stable power generation output, showing a super-strong service capability. This work not only provides a class of NBT-based piezoceramics with excellent electromechanical properties, but more importantly, the design strategy associated with double synergy effect is expected to be extended to the construction of more high-quality lead-free piezoelectric devices.