Ferroelectric and piezoelectric properties of lead-free Li0.06(K0.5Na0.5)0.94NbO3 thin films

Xinyu Bu; Changhong Yang; Mengjia Fan; Wenxuan Wang; Xiujuan Lin; Shifeng Huang

doi:10.1142/S2010135X23500091

Abstract

Lead-free (

K_{0.5}

{Na}_{0.5}

)NbO₃ (KNN) and

{Li}_{0.06}

(

K_{0.5}

{Na}_{0.5}

)

_{0.94}

NbO₃ (LKNN) thin films were fabricated by a sol-gel method. The effects of Li substitution on crystal structure, microstructure and electrical properties of KNN film were systematically studied. Li doping can enhance the ferroelectric and piezoelectric properties of KNN film. Compared with pure KNN film, the LKNN film possesses larger remanent polarization (

P_{r}

\sim

9.3

μ

C/

{cm}^{2}

) and saturated polarization (

P_{s}

\sim

41.2

μ

C/

{cm}^{2}

) and lower leakage current density (

\sim 10^{- 5}

A/

{cm}^{2}

at 200 kV/cm). Meanwhile, a typical butterfly shaped piezoelectric response curve is obtained in the LKNN film with a high piezoelectric coefficient (

d_{33}

\sim

105 pm/V). Excellent fatigue resistance (

\sim

10^{9}

switching cycles) and aging resistance (

\sim

180 days) demonstrate the long-term working stability of LKNN film. These findings indicate that KNN-based lead-free piezoelectric films have a broad application prospect in microelectromechanical systems (MEMS).