Breakdown strength and energy storage properties of epitaxial lead-based relaxor-ferroelectric films over a wide range of film thickness

Herein, we report the effect of film-thickness, ranging from 0.1 μm to 7.0 μm, on the energy storage performance of epitaxial Pb_0.91La_0.09Zr_0.7Ti_0.3O₃ (PLZT) films grown on silicon substrates. As the PLZT film-thickness increases, polarization is enhanced and reaches a maximum value at a film-thickness of 1.0 μm, while the breakdown-strength reaches its maximum value at 0.5 μm. A film-thickness of 1.0 μm achieves an optimal volumetric recoverable energy-storage density (U_r,V) of 114.4 J/cm³ and an energy-efficiency of 87.3 % at 4.7 MV/cm. Contrastingly, a film-thickness of 4.0 μm exhibits the largest stored recoverable-energy capacity over surface-area (U_r,A) of 34.2 mJ/cm² (U_r,V = 85.4 J/cm³ at 4.05 MV/cm). Moreover, a film-thickness of 4.0 μm displays a large U_r,V value of 66.8 J/cm³, good thermal stability and excellent fatigue-endurance even at an operational temperature of 200 °C. These results suggest that thick PLZT films hold promise as high-performance energy-storage capacitors capable of operating effectively in harsh conditions.