High power characterization of (Na_0.5K_0.5)NbO ₃ based lead-free piezoelectric ceramics

Though there is a lot of research related with lead-free piezoelectric materials, there are quite few research on high power characteristics of the lead-free piezoelectric materials. Especially under equilibrium conditions (continuous drive), high power characteristics in resonance and anti-resonance regions still remain unrevealed. This study investigates the high power characteristics of a sodium-potassium-niobate (NKN) based piezoelectric ceramic compared to hard lead-zirconate-titanate (PZT) under equilibrium conditions. High power characteristics were investigated with our novel high power piezoelectric characterization system (HiPoCS). (Na_0.5K _0.5)(Nb_0.97Sb_0.03)O₃ was prepared with 1.5% mol CuO addition with the mixed-oxides method. Disk-shaped samples were sintered with the conventional sintering methods. The mechanical quality factor (Q_m) at resonance (Q_a) did not possess degradation with the increasing vibration velocity (v_rms). Accordingly, it remained constant up to 0.4 m/s, which corresponds to the maximum vibration velocity (v_rms measured with 20 °C increase of the temperature on the nodal point). This behavior is superior when compared to hard-PZTs with their sharp decrease in Q_a with the increasing vibration velocity. At anti-resonance, the high power behavior trend was similar to that of at resonance. The mechanical quality factor at anti-resonance (Q_B) also remained constant up to the maximum vibration velocity (v_max = 0.4m/s). Moreover, Q_a and Q_B were in the same order up to v_max. This trend is also distinctly different than hard-PZTs and needs to be further investigated. In conclusion, NKN ceramics are capable of possessing good high power behavior at both resonance and anti-resonance modes.