Emerging ferroelectricity and piezoelectric energy harvesting properties in lead-free zinc titanate nanocrystals

Lead-free ZnTiO 3 hexagonal nanocrystals prepared by a facile hydrothermal-based synthesis process exhibit stable ferroelectricity and a high-temperature dielectric anomaly at ~ 728 K. The Curie temperature ( T c ) is associated with a probable ferroelectric (FE) to paraelectric transition from LiNbO 3 type to ilmenite phase. Direct ferroelectric measurements confirm stable and highly saturated polarization (P s ) up to 723 K, with a P s ~ 14.6 µC/cm 2 at a low coercive field of 2.3 kV/cm. Subsequently, simple, flexible piezoelectric nano (composite) generator is fabricated from ferroelectric nanocrystals with PDMS, and for 40 wt.% nanocrystals loading in the PDMS–nanomaterial composite, the device delivered an open-circuit peak voltage (V p ) of ~ 6.1 V and a short-circuit peak current (I p ) of ~ 66 nA at room temperature, when subjected to a periodic impact at 4 Hz and 15N. A steady power density of ~ 95 µW/cm 3 at 1MΩ load is delivered by a single, robust piezo device, stable up to 120 °C that exhibits excellent fatigue performance, and commendable sensitivity of ~ 0.33 ± 0.02 VN −1 (33 mVkPa −1 ) upon repeated periodic impact. The work provides a pathway towards low-cost hydrothermal-based synthesis of lead-free titanate nanomaterials with emerging ferroelectricity and understanding their structure–property relationships for exploring piezoelectric energy harvesting potential. Graphical abstract