New potassium–sodium niobate material system: a giant-d33 and high-TC lead-free piezoelectric

Abstract

In this work, we elucidate the influence of Bi_0.5Li_0.5ZrO₃ (BLZ) content on the phase structure, microstructure, and electrical properties of (1 − x)K_0.40Na_0.60Nb_0.965Sb_0.035O₃–xBi_0.5Li_0.5ZrO₃ 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.