New potassium-sodium niobate material system: a giant-d₃₃ and high-T(C) lead-free piezoelectric.

In this work, we elucidate the influence of Bi(0.5)Li(0.5)ZrO3 (BLZ) content on the phase structure, microstructure, and electrical properties of (1 -x)K(0.40)Na(0.60)Nb(0.965)Sb(0.035)O3-xBi(0.5)Li(0.5)ZrO3 lead-free ceramics. We simultaneously achieved a giant d33 and a high T(C) in this material system. The coexistence of rhombohedral and tetragonal phases is responsible for such a large d33 in the ceramics with BLZ contents (x) ranging from 0.025 to 0.035. Doping with BLZ not only induces the formation of the phase boundary, but also maintains a high T(C). The ceramic with x = 0.03 shows an enhanced piezoelectric behaviour (d33 ~ 400 pC N(-1) and k(p) ~ 0.47) together with a high T(C) of 292 °C. A good temperature stability for ferroelectricity and piezoelectricity is also observed in these ceramics. This study is the first time that such a good comprehensive performance has been obtained in potassium-sodium niobate materials. We believe that this type of material system possessing giant-d33 and high-T(C) is a promising candidate for use in high-temperature piezoelectric devices.