New Potassium–Sodium Niobate Ceramics with a Giant <i>d</i>₃₃

For potassium–sodium niobate, poor piezoelectric properties always perplex most researchers, and then it becomes important to attain a giant piezoelectricity. Here we reported a giant piezoelectric constant in (1 – <i>x</i>)­(K_0.48Na_0.52)­(Nb_0.95Sb_0.05)­O₃-<i>x</i>Bi_0.5Ag_0.5ZrO₃ lead-free ceramics. The rhombohedral-tetragonal phase boundary was shown in the ceramics with 0.04 < <i>x</i> ≤ 0.05, and then the ceramic with <i>x</i> = 0.0425 possesses a giant <i>d</i>₃₃ of ∼490 pC/N. We also discussed the physical mechanisms of enhanced piezoelectricity. As a result, such a research can benefit the sustainable development of (K,Na)­NbO₃ materials