Preparation and Characteristics of Bi0.5Na0.5TiO3 based Lead-Free thin films by Pulsed Laser Deposition

Abstract: Lead-based piezoelectric materials, such as PbZrxTi1-xO3 (PZT), have attracted considerable attention and have been widely used in actuators, sensors and transducers due to their excellent electric properties. However, considering the toxicity of lead and its oxides, environmentally friendly lead-free piezoelectric materials are attracting more attention as potential replacements for PZT. Among them, Bi0.5Na0.5TiO3 (BNT)-based materials exhibit good electrical properties and electromechanical coupling response. In this work, the 0.97Bi0.5Na0.5TiO3-0.03BiAlO3 (BNTBA) thin films (~120 nm thickness) were successfully prepared using the pulsed laser deposition (PLD) method on Pt/TiO2/SiO2/Si substrates. The effects of substrate temperature, oxygen pressure, laser repetition rate, and post-annealing treatment were investigated. X-ray diffraction (XRD) and scanning electron microscope (SEM) are used to study the structure of the films and the ferroelectric and dielectric properties are measured. The results show that it is necessary to introduce excess sodium and bismuth to compensate for their evaporation in further thermal treatment. The values of remnant polarization increase from 8.7 μC/cm2 to 12.3 μC/cm2 with the introduction BiAlO3. The dielectric constant increases from 600-550 to 710-600 and the dielectric loss increases from 4.2% to 6.7% at higher frequency when the oxygen pressure increases from 20 Pa to 30 Pa.