Significantly enhanced energy storage performance in multi-layer SrTiO3-based films via introducing a PZT polarization layer

Abstract

SrTiO₃ paraelectrics, characterised by low electrical hysteresis loss, have been extensively employed in capacitor dielectric energy storage films. However, their inherent low polarization strength limits further enhancement of energy storage density. This paper presents an STM/PZT/STM (SPS) multilayer heterostructure comprising a linear SrTi_0.99Mn_0.01O₃(STM) paraelectric layer and a PbZr_xTi_(1−x)O₃ (PZT) ferroelectric layer. By synergistically regulating the Zr⁴⁺/Ti⁴⁺ ratio and layer count within the PZT polarization layer, the multilayer film integrates STM's low-loss properties with PZT's high polarization advantage. Results indicate that when the Zr⁴⁺/Ti⁴⁺ ratio in PZT reaches 80/20 and the layer count increases to four layers (SP4S), the composite film's polarization behaviour evolves from a linear paraelectric towards a relaxor-like ferroelectric character. At this stage, the saturated polarization of the SP4S film significantly increases to 39.18 µC cm⁻², which is 7.6 times that of STM films, while retaining an exceptionally low residual polarization (1.21 µC cm⁻²). Consequently, the SP4S film achieves a high energy storage density of 52.98 J cm⁻³ and an energy storage efficiency of 86.08%, markedly outperforming existing SrTiO₃-based energy storage dielectrics. Furthermore, the SP4S film exhibits excellent fatigue resistance, temperature stability, and frequency stability, demonstrating promising application prospects.