Structural and piezoelectric characteristics of BNT–BT 0.05 thin films processed by sol–gel technique

Abstract

Polycrystalline ferroelectric lead-free (Bi 0.5Na 0.5) 0.95Ba 0.05TiO 3 (BNT–NT 0.05) thin films have been deposited on Pt/TiO 2/SiO 2/Si substrates by an optimized sol–gel/spin-coating process. The film thermal treated at 700 °C is dense and well crystallized in the rhombohedral perovskite phase. The film is composed of polyhedral shaped primary particles with an average size of approximately 35 nm, and has a smooth surface of 4.52 nm root mean square roughness (RMS). The nanoscale electrical properties of the film were investigated by piezoforce microscopy (PFM). The PFM data showed that most of the grains seem to be constituted of ferroelectric multiple domains. The maximum dielectric constant measured at zero bias voltage is about 210 and the leakage current density has a value of about 3 × 10 −5 A/cm 2 at an applied voltage about 8 V. These results indicate that, the BNT–NT 0.05 thin film is a promising functional lead-free ferroelectric material.