Unleashing the Full Sustainable Potential of Thick Films of Lead-Free Potassium Sodium Niobate (K_0.5Na_0.5NbO₃) by Aqueous Electrophoretic Deposition

Abstract

A current challenge for the fabrication of functional oxide-based devices is related with the need of environmental and sustainable materials and processes. By considering both lead-free ferroelectrics of potassium sodium niobate (K0.5Na0.5NbO3, KNN) and aqueous-based electrophoretic deposition here we demonstrate that an eco-friendly aqueous solution-based process can be used to produce KNN thick coatings with improved electromechanical performance. KNN thick films on platinum substrates with thickness varying between 10 and 15 μm have a dielectric permittivity of 495, dielectric losses of 0.08 at 1 MHz, and a piezoelectric coefficient d33 of ∼70 pC/N. At TC these films display a relative permittivity of 2166 and loss tangent of 0.11 at 1 MHz. A comparison of the physical properties between these films and their bulk ceramics counterparts demonstrates the impact of the aqueous-based electrophoretic deposition (EPD) technique for the preparation of lead-free ferroelectric thick films. This opens the door to the possible development of high-performance, lead-free piezoelectric thick films by a sustainable low-cost process, expanding the applicability of lead-free piezoelectrics.

Fabrication of Dielectric Thick Films by Electrophoretic Deposition and Their Characterization

“…Dielectric constant value of 320 (at 1 MHz) was obtained for sintered KNNT thick film. The dielectric value of the KNNT film (320) at 1 MHz was lower than the value reported for KNN thick films fabricated via electrophoretic deposition in acetone (393) [21] and aqueous media (495) [20] and the higher values of later two might be the result of dense film obtained by isostatic pressing and higher sintering temperature (1100°C). Dielectric permittivity and loss tangent (tan δ) of MgTiO 3 films were evaluated over a frequency range of 1 kHz to 1 MHz, using an impedance analyzer (HP 4284Aprecision LCR Meter).…”

“…The deposition of a negatively charged particle on anode is called anodic electrophoretic deposition and the deposition of a positively charged particle on cathode is called cathodic electrophoretic deposition. The surface charge of the particle can be easily modified by the appropriate choice of solvent or/and surfactant [18,20]. Moreover, different surface charge can be introduced on KNN particle using a single solvent with different surfactants [21].…”

Potassium‐Sodium‐Niobate‐Based Thin Films: Lead Free for Micro‐Piezoelectrics

“…They also studied the effect of post‐annealing temperature on the electric properties of 0.948(K 0.5 ,Na 0.5 )NbO 3 ‐0.052LiSbO 3 thick films. The maximum ferroelectric, dielectric, and piezoelectric properties with ε r = 1012, P r = 15.5 µC cm −2 , and d 33 = 50 pm V −1 were obtained after annealing at 800 °C for 1 h . It was demonstrated by Mahajan et al .…”

“…The maximum ferroelectric, dielectric, and piezoelectric properties with ε r = 1012, P r = 15.5 µC cm −2 , and d 33 = 50 pm V −1 were obtained after annealing at 800 °C for 1 h . It was demonstrated by Mahajan et al . that an eco‐friendly aqueous solution‐based electrophoretic deposition can be used to produce KNN thick coatings with improved electromechanical performance.…”

“…KNN‐based films have been prepared by various physical and chemical methods, and Figure b shows the distribution of the publications of KNN‐based films in the view point of synthetic techniques in recent 20 years, including pulsed laser deposition (PLD), radio frequency (RF) magnetron sputtering, chemical solution deposition (sol–gel or CSD), aerosol deposition (AD), hydrothermal (HT), reactive templated grain growth (RTGG), and metalorganic chemical vapor deposition (MOCVD) . In this section, we reviewed the development of the synthetic techniques employed for the preparation of KNN‐based films.…”