Synthesis of shape-tunable PbZrTiO3 nanocrystals with lattice variations for piezoelectric energy harvesting and human motion detection

Abstract

PbZr_0.7Ti_0.3O₃ cubes with tunable sizes and cuboids have been hydrothermally synthesized. PbZrTiO₃ cubes with three different Zr : Ti atomic percentages were also prepared. Analysis of synchrotron X-ray diffraction (XRD) patterns reveals the presence of two lattice components for these samples. Fast Fourier Transform (FFT) processing of high-resolution transmission electron microscopy (HR-TEM) images shows discernible lattice spot differences between the inner bulk and surface layer region for a PbZr_0.7Ti_0.3O₃ cube, while a cuboid has distinct lattice spot deviations. The lattice variations yield different dielectric constant numbers for these two samples, despite being bound by the same crystal faces. The PbZrTiO₃ crystals give size- and composition-dependent band gaps. Cuboids show notably larger piezoelectric and ferroelectric responses than cubes. Piezoelectric nanogenerators (PENGs) containing 30 wt% cuboids produce the highest open-circuit voltage of 20.36 V and short-circuit current of 2300 nA. The PENGs harvest energy through bending/releasing cycles to power devices and show photothermal pyroelectric activity. Moreover, a single 30 wt% cuboid PENG device integrated into a shoe insole can deliver an impressive 96.8% accuracy for human motion detection using a machine learning approach. This work illustrates that considerable lattice variation through crystal shape control is effective in enhancing material properties.