Effects of different sequence doping LiF on microstructure and dielectric properties of BCST ceramics

With the increasing focus on environmental issues, lead-free perovskite ceramics Ba_0.83Ca_0.105Sr_0.065TiO₃ (BCST) are promising candidates for dielectric and energy storage applications. To optimize the preparation process and enhance the performance of ceramics, a traditional high-temperature solid-state method has been used to fabricate BCST ceramics with 4 mol% LiF as a sintering aid added at three different sequences: before calcination (BLiFCST), after calcination (BCLiFST), and after sintering (BCSLiFT). The results indicated that all BCST-LiF ceramics exhibited a pure tetragonal perovskite structure, and LiF effectively reduced the sintering temperature from above 1250 ℃ (for pure BCST) to 1200 ℃. Among the three addition sequences, BCLiFST ceramics achieved the highest densification with dense grain arrangement and fewer surface pores. The BCLiFST ceramics also showed the optimal dielectric and ferroelectric properties: a high dielectric constant (ɛ_r = 18,114) and low dielectric loss (tanδ = 0.0103) at room temperature, along with thin-waisted hysteresis loops induced by [Li_Ti-F_O]²⁻ defect dipoles. For energy storage performance, BCLiFST ceramics exhibited a recoverable energy density of 0.15 J/cm³ and energy storage efficiency of 58% under an electric field of 28 kV/cm. These findings demonstrate that adding LiF after calcination is an effective strategy to lower the sintering temperature and optimize the comprehensive performance of BCST ceramics, providing a promising approach for the preparation of high-performance lead-free dielectric ceramics.