Performance improvement of LiF/ZnO codoped lead-free piezoelectric ceramics

Abstract

In this study, a series of Li0.058(Na0.535K0.480)0.966(Nb0.90Ta0.10)O3 (LNKNT) + (x)ZnO + (y)LiF (x = 0, 0.4, and 0.6 wt%; y = 0 and 0.2 wt%) lead-free piezoelectric ceramics were fabricated by a conventional solid-state reaction method. The codoping of ZnO and LiF could significantly improve the sintering ability of LNKNT ceramics by reducing the optimal sintering temperature from 1090 to 990 °C. The crystal phases and microstructures were analyzed by X-ray diffraction (XRD) and scanning electronic microscopy (SEM), respectively. The dielectric characteristics, electromechanical coupling factors, piezoelectric constants, and P-E curves were also measured and investigated. From the results, as 0.6 wt% ZnO and 0.2 wt% LiF were added into pure LNKNT ceramics, uniform and condensed grains can be obtained easily, and thus the sintering temperature can be decreased from 1090 °C (pure LNKNT) to 990 °C. Compared with pure LNKNT, ZnO/ LiF codoped LNKNT has better orthorhombic and tetragonal coexistence phases. In this study, the optimal d33 values were improved from 279 pC/N (pure LNKNT) to 304 pC/N (LNKNT-6Z2LF), and kp were improved from 0.46 (LNKNT) to 0.48 (LNKNT-6Z2LF). Hence, the codoping of ZnO and LiF can improve the sintering ability of the LNKNT ceramics effectively.