Piezoresponse and ferroelectric properties of lead-free [Bi[sub 0.5](Na[sub 0.7]K[sub 0.2]Li[sub 0.1])[sub 0.5]]TiO₃ thin films by pulsed laser deposition

Abstract

Polycrystalline lead-free piezoelectric [Bi[sub 0.5](Na[sub 0.7]K[sub 0.2]Li[sub 0.1])[sub 0.5]]TiO₃ (BNKLT) thin films were grown on Pt/Ti/SiO₂/Si substrates using pulsed laser deposition (PLD). In this letter, we report the ferroelectric properties and piezoresponse of the PLD-produced BNKLT thin films. X-ray diffraction characterization revealed a good crystallinity and a pure perovskite structure in the films. The films exhibited a well-defined polarization hysteresis loop with a remnant polarization P[sub r] of 13.9 µC/cm² and a coercive field E[sub c] of 10.2 MV/m. The domain structure and its thermal-driven evolution from the ferroelectric to nonferroelectric phase were observed by piezoresponse force microscopy. The results were consistent with the phase transition profile of BNKLT bulk ceramics. Typical butterfly-shaped piezoresponse loop was obtained and the effective piezoelectric coefficient d[sub 33,f] of the BNKLT thin films was about 64 pm/V.