Low temperature consolidated lead-free ferroelectric niobate ceramics with improved electrical properties

There is a concerted effort to develop lead-free piezoelectric ceramics. (Na_0.5K_0.5)NbO₃-based ceramics have good electrical properties, and are a potential replacement material for lead zirconate titanate piezoelectric ceramics. In this work a commercial powder based on (Na_0.5K_0.5)NbO₃ with an initial particle size of ∼260 nm was consolidated by spark plasma sintering (SPS). To avoid volatilization, high mechanical pressures were used to minimize the densification temperature. It was found that under a uniaxial pressure of 100 MPa, fully densified compacts can be prepared at 850 °C. Ceramics densified at such a low temperature demonstrate an unusually high remanent polarization (30 μC/cm²) and high d₃₃ (146 pC/N). The improved ferroelectric properties are ascribed to the homogeneous, dense, and submicron grained microstructure achieved.