Lead-free A2Bi4Ti5O18 thin film capacitors (A = Ba and Sr) with large energy storage density, high efficiency, and excellent thermal stability

Abstract

Lead-free thin film capacitors, simultaneously possessing a large energy storage density, ultrahigh efficiency and an extra wide working temperature range, are desirable in applications. In this work, A₂Bi₄Ti₅O₁₈ (A = Ba and Sr) thin films were successfully deposited onto Pt/Ti/SiO₂/Si by chemical solution deposition. A large energy storage density (U_re) of 37.1 and 17.2 J cm⁻³ and a high efficiency (η) of 91.5% and 80.8% were achieved in Ba₂Bi₄Ti₅O₁₈ and Sr₂Bi₄Ti₅O₁₈ thin films, respectively. Moreover, these two thin films show excellent thermal abilities under an extra wide working temperature range from −100 °C to 180 °C. Additionally, high cycling fatigue endurance with a variation of the energy storage density of less than 3.7% and efficiency less than 2.1% after 2 × 10⁸ charge–discharge cycles is obtained for these two thin films. These results indicate that A₂Bi₄Ti₅O₁₈ thin film capacitors have strong potential applications in equipment in harsh working environments.