Fabrication of Lead-Free Bi0.5Na0.5TiO3 Thin Films by Aqueous Chemical Solution Deposition

Abstract

Piezoelectric ceramics are widely used in actuator applications, and currently the vast majority of these devices are based on Pb(Zr,Ti)O3, which constitutes environmental and health hazards due to the toxicity of lead. One of the most promising lead-free material systems for actuators is based on Bi0.5Na0.5TiO3 (BNT), and here we report on successful fabrication of BNT thin films by aqueous chemical solution deposition. The precursor solution used in the synthesis is based on bismuth citrate stabilized by ethanolamine, NaOH, and a Ti-citrate prepared from titanium tetraisopropoxide and citric acid. BNT thin films were deposited on SrTiO3 and platinized silicon substrates by spin-coating, and the films were pyrolized and annealed by rapid thermal processing. The BNT perovskite phase formed after calcination at 500 °C in air. The deposited thin films were single phase according to X-ray diffraction, and the microstructures of the films shown by electron microscopy were homogeneous and dense. Decomposition of the gel was thoroughly investigated, and the conditions resulting in phase pure materials were identified. This new aqueous deposition route is low cost, robust, and suitable for development of BNT based thin film for actuator applications.

Ferroelectric and dielectric properties of Ca2+-doped and Ca2+–Ti4+co-doped K0.5Na0.5NbO3thin films

“…In this work complexes of Ca 2+ and Ti 4+ dissolved in water were used as dopants, but further doping with alkaline earth and rare earth elements should be possible. We have shown previously that aqueous precursor solutions can be applied to fabricate thin films of a whole range of different functional materials ranging from ferroelectric 74,75 , transparent conducting 76,77 and optical active materials 78 .…”

Structural and microstructural features of lead‐free BNT–BT thin films: Nanoscale electromechanical response analysis

“…26 The high compositional control required to obtain films with composition close to the MPB in these complex oxides makes chemical solution deposition (CSD) processes one of the most appropriate techniques to fabricate BNT (1-x) -BT x thin films. 27,28 Other advantages of this method include the low cost, effective to fabricate high-quality ferroelectric films with good stoichiometry control as well as a chemical homogeneity and uniform film over a large area. 27 In this context, several investigations have been conducted on BNT 1-x -BT x thin films particularly for those compositions close to the MPB.…”

Growth, Properties and Applications of Bi0.5Na0.5TiO3 Ferroelectric Nanomaterials

“…Christensen et al prepared piezoelectric BNT thin films with perovskite phase on ST and Si/Pt substrates through chemical solution deposition method. Aqueous solution containing ethanolamine, sodium hydroxide, bismuth citrate, titanium tetraisopropoxide and citric acid was utilized as the precursor [37]. Figure 1d exhibits the detailed fabrication process of the BNT films.…”

“…(c) Preparation progress of BNT films by electrophoretic deposition technology and photographs of resulted films at different applied voltages (Reproduced with permission from [36], Elsevier, 2020). (d) Fabrication schematic of BNT films through chemical solution deposition method (Reproduced with permission from [37], MDPI, 2017). (e) Preparation progress of 0.78BNT-0.22ST nanofibers by electrospinning technology, and SEM images and photograph of flexible piezoelectric 0.78BNT-0.22ST/PVDF composite membrane (Reproduced with permission from [47], Elsevier, 2016).…”