New lead-free piezoelectric thin film fabricated using metal-oxide nanosheets at low temperature

Abstract

A new lead-free piezoelectric film consisting of Sr2NaNb4O13- (SNNO-) and TiNbO5- (TNO-) nanosheets was fabricated via electrophoresis. SNNO- and TNO- films display paraelectric polarization versus electric field (P-E) loops. However, a new film composed of a mix of SNNO- and TNO- (S/T) nanosheets displayed a ferroelectric P-E hysteresis loop with large maximum polarization (18.7 mu C/cm(2)), remnant polarization (7.7 mu C/cm(2)), and a coercive electric field (86 kV/cm). The interfaces formed between the SNNO and TNO layers induced ferroelectric properties in the S/T film through the occurrence of polar distortion and octahedral tilting in the film. Ferroelectric properties were also observed in piezoelectric force microscopy images of the S/T film, which showed 90 degrees domains after the removal of the applied electric field. The dielectric constant of the S/T film was 70, which is higher than those of SNNO and TNO films, indicating that the S/T film is a ferroelectric material. The piezoelectric strain constant of the S/T film was 156 p.m./V and promising insulating properties were observed therein. The growth temperature of the S/T film was low (300 degrees C), suggesting that the S/T film can be used for flexible electronic devices.