Phase transition and piezoelectric properties of alkali niobate ceramics through composition tuning

Abstract

(1 − x)(K_0.40Na_0.60)(Nb_0.95Sb_0.05)O₃–x(Bi_0.5K_0.5)HfO₃ lead-free piezoceramics were prepared by conventional sintering method, and effects of BKH on phase transition and piezoelectric properties of the ceramics are systematically investigated. XRD as well as TEM analysis indicates rhombohedral, orthorhombic and tetragonal phase coexistence for 0.03 ≤ x ≤ 0.05 and greatly enhanced piezoelectric properties are observed in the ceramics with mixed phase coexistence regime, i.e., d^*₃₃ (∼614 pm V⁻¹) and d₃₃ (∼400 pC N⁻¹) for x = 0.035. The results show that KNNS–xBKH ceramics have potential to partially substitute PZT, and demonstrate polymorphic phase boundary (PPB) involving R phase induced by composition tuning is mostly contributed to remarkably enhanced properties of KNN-based ceramics because of lower anisotropic energy than in O–T phase coexistence PPB.