Electrical Properties and Stability Study on lead-free homo- and heterovalent substituted Bi0.5Na0.5TiO3 Thin Films for Energy Storage

Dielectric thin films have garnered considerable attention in recent years, driven by their potential applications in advanced electronics and electrical systems. This interest is particularly due to their use in the growing trend toward miniaturization, where these films play can play an important role, enabling more compact and efficient devices. In this study, we deposited xNaNbO3 – (1-x) Bi0.5Na0.5TiO3 (x = 0.22, 0.76) thin films on Pt/TiO₂/SiO₂/Si substrates using chemical solution deposition. We investigated the influence of different compositions of NaNbO3 and Bi0.5Na0.5TiO3 on energy storage and dielectric properties to evaluate the compatibility of the system. Solid solutions were successfully formed in both systems, exhibiting a pure perovskite phase and very low surface roughness. The Bi0.5Na0.5TiO3- and NaNbO3-based capacitors demonstrated dielectric breakdown strengths of 1.5 MV cm^-1 and 1.2 MV cm^-1, respectively, with recoverable energy densities of 18 J cm^-3 and 10 J cm^-3. Although the efficiencies were low around 60% and 50% at maximum field, as well as the polarization hysteresis at fields above 700 kV cm^-1 suggesting leakage current contributions, both systems showed impressive temperature stability and relative permittivity. The energy storage properties remained stable from 25 to 175°C for x = 0.22 and from 25 to 275°C for x = 0.76, with cyclic fatigue stability maintained up to 10⁷ cycles. These results pave the way for integrating this binary material system into other BNT-substituted systems to enhance temperature and cyclic fatigue stability.