Defect-relevant piezoelectric and ferroelectric properties in LiCuTa3O9-doped K0.5Na0.5NbO3 lead-free piezoceramics

摘要： Lead-free K0.5Na0.5NbO3 + x mol LiCuTa3O9 (abbreviated to KNN-xLCT) piezoceramics are synthesized via a conventional sintering technique. All ceramics exhibit perovskite structure and their densification is improved after the addition of LCT. The doping of small quantities of LCT (x ≤ 0.015) results in the generation of two sorts of defect complexes [i.e., ?? V??(Cu???o ) ], inducing greatly hardening electrical behaviors with high mechanical quality factor Qm of ~ 780 at x = 0.015. However, excess LCT (x ≥ 0.015) contributes to the substantial reduction of defect complexes, and thus the ceramics are softened, presenting a relatively low Qm of ~ 480 at x = 0.03. It is noted that the ceramics with x = 0.03 remain comparatively great piezoelectric performances: d33 = 96 pC/N and kp = 37%. Our study indicates that the electrical properties of KNN-based ceramics doped with LCT are closely related with microscopic defect structure in the materials.