ABSTRACT: Solid-state refrigeration based on caloric effect (CE) holds out promise for environmentally friendly cooling with high energy-efficiency and downsize scalability, however, their comprehensive refrigeration performance is notably inferior in comparison to commercial refrigerant due to the lack of scientiffc guidance for material discovery and performance improvement. In this talk, we propose a general approach to investigate refrigeration performance of CE materials under external fields (electric, magnetic, mechanical) near phase transition temperature (Tc), with its efficiency surpassing traditional methods by one to two orders of magnitude. Through analysis of the evolution of microscopic dynamics, we clarify that the refrigeration process mainly involves heat absorption by a transition from a low-potential-energy to a high-potential-energy state driven by external field. Using electrocaloric effect (ECE) PbTiO3 (bulk) and GeS (two-dimensional) as representative prototypes, we demonstrate the field-dependent isothermal entropy change ΔS, adiabatic temperature change ΔT and coefficient of performance (COP) near Tc, along with comparison with results from indirect method and experiment measurements. As a further step, we showcase the investigation and regulation of CE in multicaloric refrigeration process. This work establishes an effective and universal method for predicting key refrigeration parameters, which can be applied to extensive caloric materials, that provide important insights for material design in solid-state refrigeration technology.
Keywords: solid-state refrigeration, electrocaloric effect, isothermal entropy change, adiabatic temperature change, multiscale simulation, thermal hysteresis and transport, machine learning
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Prof. Wang has completed his PhD from Institute of Metal Research, Chinese Academy of Sciences and Postdoctoral Studies from University of California, Irvine, U.S.A. He is the Dean of department of physics of Central South University, vice Dean of Provincial key Lab. He has published more than 100 papers in reputed journals, including Nature, Nature Materials, Nature Nanotechnology, Nature Communications and Physical Review Letters, Physical Review B, Applied Physics Letters, etc, and has been serving as an editorial board member/editor in MGE Advances, Info. Funct. Mater. and Font. Phys, etc.