A review on (Sr,Ca)TiO3-based dielectric materials: crystallography, recent progress and outlook in energy-storage aspects

In pursuit of developing high-performance lead-free energy storage capacitors, strontium titanate (SrTiO3) and calcium titanate (CaTiO3) are widely recognised as promising dielectric ceramics. Both end members are completely miscible for the entire doping concentration which results in the successful formation of (Sr1 − xCax)TiO3 solid solutions. Most importantly, the Ca dopant irons the electric fields, temperature and frequency stabilities of SrTiO3 ceramic. This review encompasses up to date knowledge of crystallography, dielectric properties and recent progress on energy storage aspects of various (Sr1 − xCax)TiO3 materials. Firstly, the structural phase transition (with special attention to room temperature) behaviour has been discussed which is essential to understand the origin of functional dielectric properties. Thereafter, various strategies to improve the energy storage properties of bulk (Sr1 − xCax)TiO3-based materials have been discussed. Further, leverage of the improved properties in the bulk ceramics into the thin film regime will be essential for creating next-generation high-performance power electronic devices. In this perspective, some interesting developments reported in thin film form are also discussed. Finally, challenges and outlook of (Sr1 − xCax)TiO3-based bulk ceramics and thin films towards future research and the applications are presented.