Optimized microstructure and enhanced breakdown strength in Ca1−xSrxTiO3 solid solutions

Linear dielectric materials are ideal options for energy storage application due to the typical high energy storage efficiency and breakdown strength. In the present work, linear dielectric system Ca_1-xSr_xTiO₃(x=0~0.6) was synthesized through conventional solid state reaction method. All the samples were sintered at 1400°C and had dense and pore-free microstructures. The effects of Sr substitution on the phase transition, microstructure and ferroelectric properties were systematically investigated. Slow scanning X-ray diffraction showed that crossover region between orthorhombic phase (Pbnm) and tetragonal phase (I4/mcm) at about x=0.30-0.50 has been obtained. SEM revealed the Ca_0.6Sr_0.4TiO₃ ceramics exhibit the most homogeneous microstructure with fine grains. The breakdown strengths were found to be enhanced near the phase transition composition due to the optimized microstructure, Ca_0.6Sr_0.4TiO₃ showed the highest breakdown strength, which reached 26 kV/mm at room temperature. Additionally, HfO₂, with a high band energy, was selected as additive into the Ca_0.6Sr_0.4TiO₃ system to mitigate the high-temperature and high-field loss, so that to improve the stability of energy storage efficiency under elevated temperature and electric field.