Optimizing the electrocaloric effect by ab initio based simulations: The benefits of substitution

We study the impact of Sr substitution on the electrocaloric effect (ECE) of BaTiO3 by means of ab initio based molecular dynamic simulations. The conventional ECE is maximal at the paraelectric to ferroelectric phase transition and the inverse ECE occurs at the ferroelectric to ferroelectric phase transitions for all concentrations. These ECE peaks are systematically shifted to lower temperatures with increasing Sr concentration. This allows to enhance the ECE at and below room temperature. While the conventional ECE in the system is promising for multi-stack cooling devices, first results on concentration graded multilayers show that the internal boundary conditions may strongly reduce the response.