Fabrication of lead-free ferroelectric (Na,K)NbO3 thin films by pulsed laser deposition

We fabricated (Na
_1-x
K
_x
)NbO
₃
(NKN) thin films with x=0.1 (NKN10), 0.2 (NKN20) and 0.3 (NKN30) on SrTiO
₃
(STO) substrate by pulsed laser deposition (PLD). NKN ceramics were prepared by modified solid-state reaction method, and NKN thin films were fabricated using this ceramics target by PLD. The NKN films were epitaxially grown on (001), (110) and (111) STO substrates. The NKN films on (001) STO had a smooth surface, the films on (110) STO had a striped pattern, and the films on (111) STO had trigonal pyramid-like structure. It was observed that remanent polarizations of the films increased with increasing K content. The P-E hysteresis of NKN30 film on (111) STO substrate showed a very large hysteresis loop with a remanent polarization P
_r
of 69 μC/cm
²
.