Aqueous chemical solution deposition of lead-free piezoelectric thin films

The last decade has seen a considerable effort in development of lead-free alternatives to lead zirconate titanate (PZT) based piezoelectric materials. Several approaches to enhance the piezoelectric properties of lead-free... [ view full abstract ]

The last decade has seen a considerable effort in development of lead-free alternatives to lead zirconate titanate (PZT) based piezoelectric materials. Several approaches to enhance the piezoelectric properties of lead-free ceramics have been investigated, categorized as either compositional engineering (e.g. doping) or microstructural engineering (e.g. grain texture or oriented films) to enhance the piezoelectric properties. Here we present development of aqueous solution-based processing routes to a selection of lead-free piezoelectrics thin films on different types of substrates. Aqueous chemical solution deposition is a simple, environmental friendly and highly flexible route to oxide thin films and is the main film synthesis platform in our group. One of our recent studies on Bi_0.5Na_0.5TiO₃ thin films [1], highlights the need for precise control of the processing parameters to obtain phase pure and oriented thin films. Performing ex situ studies are time consuming and might not give the complete picture, and a cell for in situ X-ray diffraction studies with atmospheric control for the pyrolysis step during chemical solution deposition of thin films has been developed. Understanding the evolution of the nucleation and crystallization of the thin films will guide designing of the optimal procedure for fabrication and tuning the desired piezoelectric properties. We report on successful fabrication of (K_0.5Na_0.5NbO₃ (KNN), BaTiO₃-based, Ba_1-xSr_xNb₂O₆ and Bi_0.5Na_0.5TiO₃ (BNT)) thin films by the aqueous chemical solution deposition. These new aqueous solution deposition routes are low cost, robust, and suitable for implementation of lead-free materials in different applications. The piezo- and dielectric properties will be discussed in relation to the nucleation and growth kinetics, orientation of the film as well as type of substrate.

1.   Christensen, M., M.-A. Einarsrud, and T. Grande, Fabrication of Lead-Free Bi_0.5Na_0.5TiO₃ Thin Films by Aqueous Chemical Solution Deposition. Materials, 2017, 10, p. 213.