Piezoelectric power generation of vertically aligned lead-free (K,Na)NbO3 nanorod arrays

We report piezoelectric power generation at room temperature, as well as at elevated temperature, using vertically aligned lead-free (K,Na)NbO3 nanorod arrays on a conducting substrate. Ferroelectric (K0.6Na0.4) NbO3 nanorod arrays having a high piezoelectric coefficient of ca. 180 pm V-1 were epitaxially grown on a conducting SrRuO3/SrTiO3 substrate via the facile hydrothermal method at low temperature (ca. 190 degrees C). After electric poling, the (K,Na)NbO3 nanorod array-based nanogenerator generated a stable high power density of similar to 101 mu W cm(-3) at 20 degrees C, almost 16 times greater than a BaTiO3 nanowire-based vibrational energy harvester (ca. 6.27 mu W cm(-3)). The (K,Na)NbO3 nanorod array-based nanogenerator exhibited little frequency dependence on external force over a relatively low-frequency range (<= 10 Hz) and showed long-term durability even at 100 degrees C, with a power density of 29 mW cm(-3). This work demonstrates the potential of eco-friendly nanogenerators based on (K,Na)NbO3 nanorod arrays for high-output power generation under various environmental conditions.