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Reversible and irreversible colossal barocaloric effects in plastic crystals

Accepted version
Peer-reviewed

Type

Article

Change log

Authors

Aznar, A 
Lloveras, P 
Barrio, M 
Negrier, P 
Planes, A 

Abstract

The extremely large latent heat exchanged in phase transitions involving strong molecular orientational disordering has recently led to the proposal of plastic crystals as a feasible solution for solid-state barocaloric eco-friendly cooling technologies. Here we determine the reversible barocaloric response of four plastic crystals derived from neopentane [C(CH3)4]: (NH2)C(CH2OH)3 (TRIS for short), (NH2)(CH3)C(CH2OH)2 (AMP), (CH3)C(CH2OH)3 (PG) and (CH3)3C(CH2OH) (NPA). All of them display colossal entropy changes at their ordered-plastic phase transition, which is a primal requirement for competitive barocaloric materials. However, we show that it is also important to verify that the large barocaloric effects can be achieved using pressures that, while being moderate, are large enough to overcome the pressure-dependent hysteresis. From this quantity and using the quasi-direct method, we determine the minimum pressure needed to achieve reversible barocaloric effects, prev, for each compound. Specifically, we find a small and moderate prev for PG and NPA, respectively, which therefore display colossal reversible barocaloric effects comparable to harmful fluids used in current refrigerators and thus confirm the potential of plastic crystals as excellent alternatives. Instead, in TRIS and AMP, the obtained prev is excessive to yield reversible barocaloric effects useful for cyclic applications.

Description

Keywords

3403 Macromolecular and Materials Chemistry, 34 Chemical Sciences

Journal Title

Journal of Materials Chemistry A

Conference Name

Journal ISSN

2050-7488
2050-7496

Volume Title

8

Publisher

Royal Society of Chemistry

Rights

All rights reserved
Sponsorship
Engineering and Physical Sciences Research Council (EP/M003752/1)
European Research Council (680032)
This work was supported by the MINECO projects MAT2016-75823-R and FIS2017-82625-P, the DGU project 2017SGR-42, the UK EPSRC grant EP/M003752/1, and the ERC Starting grant no. 680032. X. M. is grateful for support from the Royal Society.