Hae Jin Seog

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 °C). After electric poling, the (K,Na)NbO3 nanorod array-based nanogenerator generated a stable high power density of ∼101 μW cm−3 at 20 °C, almost 16 times greater than a BaTiO3 nanowire-based vibrational energy harvester (ca. 6.27 μW 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 °C, with a power density of 29 μW 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.

Effect of Ta content on the phase transition and piezoelectric properties of lead-free (K0.48Na0.48Li0.04)(Nb0.995-xMn0.005Tax)O3 thin film

Lead-free (K0.48Na0.48Li0.04)(Nb0.995−xMn0.005Tax)O3 (abbreviated KNL-NMT-x, x = 0 ∼ 0.20) thin films were prepared using a chemical solution deposition method, and the effects of Ta content on the structural, dielectric, ferroelectric, and piezoelectric properties were investigated. X ray diffraction results indicate that the phase structure of KNL-NMT-x films undergoes a transition from orthorhombic to pseudocubic phase with increasing Ta content. The substitution of Ta5+ for the Nb5+ site in the KNL-NMT-x films produced to the relaxor-like ferroelectric with a diffuse phase transition. The KNL-NMT-0.10 thin film at the orthorhombic-pseudocubic phase boundary showed optimum dielectric and piezoelectric properties; dielectric constant ɛr = 2650, Curie temperature Tc = 323 °C, remnant polarization Pr = 16.1 μC/cm2, coercive field Ec = 22.2 kV/cm, and effective piezoelectric coefficient d33,f = 61 pm/V.