Ultrahigh piezoelectric coefficients of Li-doped (K,Na)NbO3 nanorod arrays with manipulated O-T phase boundary: Towards energy harvesting and self-powered human movement monitoring

Abstract

Lead-free piezoelectric one-dimensional (1D) nanostructures have exhibited great potential in building biocompatible micro/nano-energy harvesters and self-powered smart sensors. However, their low piezoelectric coefficient still remains as the biggest obstacle for practical applications. In this work, an ultrahigh piezoelectric coefficient with calibrated d 33 from 400 pm V -1 to 814 pm V -1 is achieved in Li-doped (K,Na)NbO 3 (KNLN) lead-free piezoelectric nanorod arrays (NRAs). The giant enhancement on the piezoelectric performance of the KNLN nanorods can be attributed to the manipulation on the phase transition behavior together with the relaxation of strain. The Li + dopants induce large NbO 6 octahedral distortion and result in the decreased phase transition temperature from orthorhombic (O) to tetragonal (T) phase, which leads to the construction of the O-T phase boundary at room temperature and improves the polarization performance of the products. The ultrahigh piezoelectric performance of the KNLN NRAs gives rise to the remarkably improved energy harvesting performance, which shows highly sensitive pressure sensing behaviors and can be utilized for monitoring the human-body motions. Giant piezoelectric coefficient d 33 up to 814 pm V -1 is achieved in lead-free (K,Na,Li)NbO 3 nanorod arrays by manipulating the orthorhombic-tetragonal phase boundary through A-site Li-doping. The KNLN nanorod arrays exhibit outstanding piezoelectric energy harvesting and pressure sensing performances and realize the self-powered monitoring of human body motions for smart analyzing of the human movement behaviors. • Li-doped (K,Na)NbO 3 nanorod arrays were grown by hydrothermal process. • Giant piezoelectric coefficient d 33 ~ 814 pm V − 1 is achieved in KNLN nanorod arrays. • Orthorhombic-tetragonal phase boundary of KNLN nanorods is constructed at RT. • The nanogenerators exhibit outstanding energy harvesting and sensing performance. • Self-powered human-body-movements monitoring is realized by KNLN nanogenerators.