Superior piezoelectric performance in high-TC sodium–bismuth titanate ferroelectric ceramics through spark plasma sintering

High-performance piezoelectric ceramics with excellent thermal stability are essential for high-temperature sensor applications. However, conventional fabrication methods offer limited improvements in piezoelectric performance. In this study, a significant enhancement in the piezoelectric performance of highly textured sodium–bismuth titanate (Na_0.5Bi_4.5Ti₄O₁₅, NBT) ceramics was achieved using the spark plasma sintering (SPS) method. The textured NBT ceramics exhibited a high degree of (00l) orientation, with a Lotgering factor of 82%, a superior piezoelectric constant d₃₃ of 35.8 pC N⁻¹, more than twice that of the ordinary sintered (OS) NBT (15.8 pC N⁻¹), and a high Curie temperature T_C of 661 °C. Microstructural analysis, domain characterization, and electrical property evaluation confirmed that polarization switching is more efficient in the textured ceramics, as demonstrated by scanning electron microscopy (SEM), piezoresponse force microscopy (PFM), and polarization–electric field (P–E) hysteresis loops. The direct-current (DC) resistivity of textured ceramics was significantly enhanced due to reduced bismuth volatilization and lower oxygen vacancy concentrations. Notably, the textured NBT ceramics exhibited outstanding thermal stability, with only a 17% variation in d₃₃ from room temperature to 500 °C, while maintaining a high DC electrical resistivity of 1.45 × 10⁶ Ω cm at 500 °C. This study not only underscores the potential of textured NBT ceramics for high-temperature piezoelectric sensors but also demonstrates an effective strategy for enhancing the piezoelectric properties of ceramic materials through spark plasma sintering.