Microstructure and electrical properties of 3-0 type composite of Na_0.5Bi_2.5Nb₂O₉-based bismuth-layered piezoceramics

The microstructure and electrical properties of 3-0 type composite of Na_0.5Bi_2.5Nb₂O₉-based bismuth layered piezoceramics modified by Al₂O₃ addition are investigated. The darker and plate-like grains, locating at the grain boundaries, are confirmed to be pure α-Al₂O₃ by high resolution transmission electron microscope, not a Bi₂AlNbO₇ pyrochlore phase. This 3-0 type Na_0.5Bi_2.5Nb₂O₉-Al₂O₃ composite piezoceramics have a large piezoelectric constant d₃₃ of 15.2pC/N with good temperature stability up to 600 °C, and good ferroelectric properties with a relatively large remnant polarization of ~11.6 μC/cm². These demonstrate that designing a 3-0 type composite structure would be an effective approach to tailor the microstructure and improve the electrical properties of bismuth layered piezoceremics for their potential applications at temperature up to 600 °C.