Public Lecture: "Colossal pressure-induced caloric effects in plastic crystals for solid-state cooling"

29 July 2019

"Colossal pressure-induced caloric effects in plastic crystals for solid-state cooling"

"Colossal pressure-induced caloric effects in plastic crystals for solid-state cooling"

Dr. Pol Lloveras , Polytechnic University of Catalonia

Our modern welfare requires refrigeration as evidenced by billions of cooling units installed around the world, a number which is expected to continue to increase markedly due to emerging middle classes and more extreme temperatures caused by global warming. Such technologies are based on pressure-driven evaporation, which therefore permit to control the exchange of the latent heat using external work. However, the fluids used therein are mostly hydrofluorocarbons (HFCs) with a huge greenhouse potential, which poses a serious environmental problem. Alternatives based on solid-state first-order phase transitions that are sensitive to an external field such as magnetic, electric or mechanic, have been explored, but the magnitude of the latent heat associated with such transformations is usually substantially smaller compared to evaporation. Here it will be shown that the pressure-driven caloric response (i.e. barocaloric effect) at phase transitions undergone by some plastic crystals is comparable to that in HFCs due to an unusual molecular orientational disordering and, therefore, it represents an important advance towards the development of environmentally friendly solid-state barocaloric cooling devices. The obstacle set out by the transition hysteresis for the reversible caloric response obtained upon cyclic application and removal of pressure will also be discussed as this is key for technological implementation.

Pol Lloveras received his Ph.D. in Condensed Matter Physics from the University of Barcelona (Spain) in 2010 with modeling studies on ferroelastic and magnetostructural systems. After a first postdoc in the École Polytechnique (France), in 2012 he joined the Group of Characterization of Materials at the Universitat Politècnica de Catalunya (Spain) where he has specialized in high-pressure techniques and pressure-driven caloric (i.e. barocaloric) effects. He has also been Research Associate at the University of Cambridge. Recently, he has analyzed the barocaloric response of a wide range of materials including antiferromagnets, ferroelectrics, superionic conductors and plastic crystals. His current research interests focus on the realization of unprecedented calorimetric experiments under simultaneous application of pressure and electric field.

Date: Thursday, 5 September 2019
Time: 11am - 12pm AEST
Location: OMB G32, Old Main Building (K15), UNSW Sydney