Broad implementation of the Internet of Things, portable electronics or inside-the-body sensors has been hindered by the limitations of conventional batteries. Advances in energy harvesting can play a crucial role towards the application of those technologies. This includes piezoelectric energy harvesting for the use of local mechanical vibrations and their transformation into electrical sources for low-power electronics. For this purpose, innovative engineered materials with high piezoelectric response and capable to work at low frequencies are required.
In this research, we show our progress in the development of Niobium-doped Pb(Zrx-1Tix)O3 ceramics (PNZT), close to the so-called Morphotropic Phase Boundary (MBP), containing ZrO2 micro particles. Characterization via Scanning Electron Microscopy and Electron Backscatter Diffraction (EBSD) revealed a preferential orientation of the PNZT grains distinctive of textured ceramics, which are usually obtained with more complex techniques, such as templated grain growth (TGG) and tape casting. Despite that X-ray diffraction showed a single tetragonal perovskite phase, which is typically related with lower electromechanical properties, further characterization uncovered high piezoelectric coefficient d33 ~ 1000 pm/V at frequencies up to 1 Hz and a piezoelectric voltage constant g33 ~ 34 x 10-3 Vm/N. By decreasing the dimension of the ZrO2 particles, a systematic appearance of the monoclinic phase was found accompanied by a decrease of the piezoelectric properties. Therefore, a PNZT-ZrO2 composite that displays high piezoelectric behavior at low frequencies has been fabricated by a simple and inexpensive method, compared to other highly-oriented ceramics. Understanding of the mechanisms that are responsible for such improvement in the piezoelectric performance would help the application of this methods to other (lead-free) materials, making it promising for energy harvesting applications.