Improving the ferroelectric and dielectric properties of barium strontium titanate thin films via local chemical design

Ferroelectric thin films have gained significant attention in recent years due to their potential applications in electronic devices such as ferroelectric memories, phase shifters, filters, and energy storage capacitors. In the present study, a local chemical design strategy was employed to enhance the ferroelectric and dielectric characteristics of Sr_0.6Ba_0.4TiO₃ thin films. The samples were prepared using the chemical solution deposition technique, with Bi³⁺ ions being introduced into the A-sites. As the concentration of Bi³⁺ ions increased, both the maximum polarization and the recoverable energy storage density showed a gradual rise, reaching values of 11.77 μC cm⁻² and 4.19 J cm⁻³, respectively, under an applied voltage of 30 V. Notably, the dielectric constant exhibited an enhancement of over 3 times while maintaining a low dielectric loss (<0.06) for the composition of (Sr_0.6Ba_0.4)_0.7□0.1Bi_0.2TiO₃ and (Sr_0.6Ba_0.4)_0.55□0.15Bi_0.3TiO₃. First-principles calculations demonstrated that substituting Ba²⁺ and Sr²⁺ ions with Bi³⁺ ions in Sr_0.6Ba_0.4TiO₃ thin films led to greater off-center displacements of cations, thereby improving the polarization and dielectric constant. The introduction of Bi³⁺ ions also significantly stabilized the dielectric constant, with the temperature coefficient of capacitance varying by less than 6.8% over the range of 25–300 °C. Furthermore, the dielectric constant exhibited minimal hysteresis, along with high dielectric tunability (>20%) and low dielectric loss (<0.02) under a low applied voltage of 12 V. This study provides a promising approach for enhancing the ferroelectric and dielectric properties of lead-free dielectric materials.