Domain configuration and piezoelectric properties of (K0.50Na0.50)1−xLix(Nb0.80Ta0.20)O3 ceramics

Domain structure plays an important role in determining piezoelectric properties of ferroelectric materials. However, limited studies have been carried out on the domains of (K,Na)NbO3-based lead free ceramics. The domain configuration, domain reversal behavior and piezoelectric properties of (K0.50Na0.50)1−xLix(Nb0.80Ta0.20)O3 (KNN-Lix) ceramics with x = 0.02, 0.035 and 0.05, were studied in this research. It was observed that ceramics with different phases show distinctly different domain configurations and domain reversal behaviors. When compared to other two compositions, x = 0.035 with coexistent orthorhombic-tetragonal phases at room temperature was found to possess curved domain stripes and larger average domain width, leading to optimal piezoelectric properties with d33* = 260 pm/V and kp = 48%. Based on the microstructures, polarization hysteresis loops and unipolar strain curves under high electric field, it was concluded that the larger domain size and easier domain switching are due to the coexistence of orthorhombic and tetragonal phases, account for the improved properties in KNNT-Li0.035 ceramics.