Sodium potassium niobate (K0.5Na0.5NbO3, KNN) thick films by electrophoretic deposition

Abstract

K_0.5Na_0.5NbO₃ (KNN) is one of the most promising lead free compositions to substitute lead based piezoelectrics. Due to size and functionality demands, thick films are currently required for specific electroceramics applications. However, what is lacking is the exploitation of low cost, solution-based processes for the fabrication of KNN thick films that are versatile and easy to scale up, such as electrophoretic deposition (EPD). In this article, KNN thick films with thicknesses ranging from 10–60 μm, prepared by EPD on platinum substrates, are reported. The films are made from acetone with triethanolamine suspension media. When sintered at 1100 °C/2 h they possess relative permittivity and dielectric loss of ∼393 and ∼0.07, respectively, at room temperature and at 1 MHz. KNN films show piezoelectric response (d₃₃) of ~40 pC N⁻¹. It is notable that such values are comparable to the properties of equivalent bulk ceramics. The study of the relationships between processing variables and the films' properties shows that, through a simple and yet low cost process such as EPD, thick KNN films can be consistently designed to be suited to the required application. These results suggest that this fabrication method is very promising as a core technology for low-cost and high-performance KNN thick films.