SCOPE · Solid-state cooling under pressure and electric field: novel multicaloric strategies to improve material performance

There is an increasing need to find novel and sustainable alternatives to current dominating cooling systems. These systems are based on the compression and expansion of powerful greenhouse polluters and thus contribute notably to global warming when released to the atmosphere. Caloric materials, which display thermal changes upon variations on the corresponding applied field, are promising candidates because 1) they can be energy efficient and 2) do not compel the direct use of greenhouse gases. Among the different caloric families, those sensitive to hydrostatic pressure (barocalorics (BC)) are of particular interest because of the wide range of candidates, their very large caloric effects and no mechanical breakdown. Nevertheless, BC materials suffer from high intrinsic irreversibilities that limit their caloric efficiency. Interestingly, some BC materials exhibit ferroelectric transitions that make them sensitive to the application of electric fields and, hence, display electrocaloric (EC) effects as well. The goal of this MSCA project is thus to take advantage of multicaloric effects to improve the caloric performance in polar barocaloric materials. To do so, for the first time we will simultaneously apply pressure and an electric field to these materials by performing unprecedented experiments of calorimetry and dielectric spectroscopy under these two fields. From these measurements, we will be able to define novel multicaloric routes to enhance the reversibility and, thus, report improved caloric performances. Additionally, a detailed characterisation of the lattice dynamics will be performed to understand the physical origin of these novel multicaloric strategies. This proposal joins the expertise in barocalorics of the Host Group and the expertise in electrocalorics of the Applicant. The successful achievement of our proposal will represent a breakthrough in the material science community, both at the fundamental and applied level.