Electrocaloric multilayer cooling device concepts

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Ferroic cooling exploits electric field-driven entropy changes near phase transitions in solid-state materials. It is considered an exceptionally energy-efficient and environmentally friendly cooling technology. Since electrical energy is ubiquitously available, in particular the electrocaloric (EC) cooling effect seems to have the highest potential for being used in future everyday devices.Theoretical studies in the first funding period have clearly shown that the material for EC cooling devices should make be of relaxor-type, that it should be composed stoichiometrically, dense and poreless to apply high electric field strengths and that it should be very thin. Relaxor thin films meet these requirements at the best.For that reason, we continue to study BaTiO3-based materials which are environmentally friendly lead-free materials allowing such high electric fields. In particular, (Ba,Sc,Ca)(Ti,Zr)O3:Mn and (Ba,Sc,Ca)(Ti,Sn)O3:Mn remain in the focus of our work because they show large EC activity in a broad temperature range. We adjust the composition of these thin films easily by multi-target sputtering where the power of each target is controlled separately. Furthermore, multi-target sputtering enables large-scale production on stiff and on flexible substrates as well as reel-to-reel deposition.In particular, the proposal for the second funding period focuses on material development and optimization, on fabrication and evaluation of multilayer stacks with embedded electrodes, on the concept of multilayer EC cooling devices and on the fabrication and evaluation of an EC cooling demonstrators.