Phase transition characteristics and associated piezoelectricity of potassium-sodium niobate lead-free ceramics

Abstract

To achieve high piezoelectric activity and a wide sintering temperature range, the ceramic system concerning (1 − x)(K_0.48Na_0.52)(Nb_0.96Sb_0.04)O₃–x[Bi_0.5(Na_0.7Ag_0.3)_0.5]_0.90 Zn_0.10ZrO₃ was designed, and the rhombohedral–tetragonal (R–T) phase boundary can drive a high d₃₃. Phase transition characteristics as well as their effects on the electrical properties were investigated systematically. The R–T coexistence phase boundary (0.04 ≤ x ≤ 0.05) can be driven via modification with BNAZZ, and has been confirmed by XRD and temperature-dependent dielectric constants as well as Raman analysis, and the ceramics possess enhanced piezoelectric properties (d₃₃ ∼ 425 pC N⁻¹ and k_p ∼ 0.43) and a high unipolar strain (∼0.3%). In addition, a wide sintering temperature range of 1050–1080 °C can warrant a large d₃₃ of 400–430 pC N⁻¹, which can benefit practical applications. As a result, the addition of BNAZZ is an effective method to improve the electrical properties (piezoelectricity and strain) and sintering behavior of potassium-sodium niobate ceramics.