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New concepts for cooling: Origins of the inverse electrocaloric effect
- Date: 20.10.2022
- Place: Kolloquium des Internationalen Graduiertenkollegs Energy Conversion Systems (IGK 2495), FAU Erlangen, Germany
Ferroic cooling is promising for sustainable and noise-reduced solid state cooling devices. In particular first-order phase transitions in ferroelectric, ferroelastic and ferromagnetic materials allow for giant isothermal entropy or adiabatic temperature changes. Commonly, the conjugate field is applied to reduce the entropy of the system (conventional caloric effect). However, in some cases also inverse caloric effects occur. It is thus important to fundamentally understand the factors promoting large conventional and inverse responses.
In this talk I will mainly focus on the electrocaloric effect in the prototypical ferroelectric material BaTiO3. I will analyze the conditions giving rise to large caloric responses based on an effective Hamiltonian derived from first principles. I will show how the combination of field protocol and materials optimization by substitution and strain allows to taylor sign and magnitude of the caloric response.