Abstract
Piezoceramics for high-power applications require both high piezoelectric coefficient (d(33)) and mechanical quality factor (Q(m)). However, the trade-off between them poses a significant challenge in achieving high values simultaneously, which is more prominent in lead-free piezoceramics. Here, we propose a new strategy, local Cu-acceptor defect dipoles embedded orthorhombic-tetragonal phase boundary engineering (O-T PBE), to balance d(33) and Q(m) in potassium sodium niobate piezoceramics. This is validated in 0.95(K(0.48)Na(0.52))NbO(3)-0.05(Bi(0.5)Na(0.5))HfO(3)-0.2%molFe(2)O(3)-xmol%CuO ceramics. Our strategy simultaneously maintains the O-T PBE and introduces local dimeric (CuNb″'-VO∙∙)' and trimeric (VO∙∙-CuNb″'-VO∙∙)∙ defects. The dimeric defects form defect dipole polarization that pins domain wall motion, while the trimeric ones introduce the local structural heterogeneity that leads to nano-scale multi-phase coexistence and abundant nano-domains. Encouragingly, for the Cu-doped sample with x = 1, Q(m) increases by a factor of 4, but d(33) only decreases by 1/5 (i.e., achieving a d(33) of 340 pC/N and a Q(m) of 256). Our research provides a new paradigm for balancing d(33) and Q(m) in lead-free piezoceramics, which holds promise for high-power applications.