Effects of dwell time during sintering on electrical properties of 0.98(K_0.5Na_0.5)NbO₃-0.02LaFeO₃ ceramics

The effects of dwell time on the phase structure, microstructure, and electrical properties were investigated for the 0.98(K_0.5Na _0.5)NbO₃-0.02LaFeO₃ ceramics (abbreviated as 0.98KNN-0.02LF). All the ceramics sintered for different dwell time are of pure phase and the peak intensity of the 0.98KNN-0.02LF ceramics becomes stronger with a longer dwell time. Denser microstructures with larger grain size are developed for the sample with a longer dwell time. The maximum dielectric permittivity decreases with increasing the dwell time, and the deteriorative dielectric properties are due to the increasing grain size and the domain wall motion. Ferroelectric properties results indicate that 2P_r value slightly decreases with increasing the dwell time, while the 2E_c value increases. Consequently, the 0.98KNN-0.02LF ceramic sintered at 1150 C for 2 h shows optimum dielectric properties (É"_r=2253 and tan δ<5%) and ferroelectric properties (2P_r=34.51 μC/cm² and 2E_c=5.07 kV/mm).