Barocalorics emerging as an environmentally friendly alternative to greenhouse gas producing refrigerants
DOI: 10.1063/10.0004909
Barocalorics emerging as an environmentally friendly alternative to greenhouse gas producing refrigerants lead image
Despite efforts to phase out greenhouse gas producing refrigerants, they’re still widely used. David Boldrin provides an overview on how barocaloric materials could provide a viable environmentally friendly alternative.
Barocalorics, which undergo large temperature changes when hydrostatic pressure is applied, are part of the family of solid-state caloric materials that respond to external magnetic, electric, or mechanical forces.
The barocaloric effect (BCE) can be related to the degrees of freedom (DOF) within a material. The larger the DOF change as a result of applied pressure, the larger the BCE will be. Because there are many forms of DOF (e.g., structural, magnetic), barocaloric effects can be found in a wide variety of materials, with many opportunities to optimize them to increase their cooling properties.
Until recently, barocalorics have not been considered advantageous due to the large pressure required to induce an adequate cooling effect. However, researchers produced record-breaking BCEs under low pressures in materials such as plastic crystals, with BCEs 10 times higher than in other materials.
In his research, Boldrin is exploring how antiperovskite materials, such as a manganese-nickel-nitrogen compound (Mn3NiN), can be tuned to increase the BCE. These antiperovskites, characterized by complex magnetic structures, are similar to perovskites except their anions and cations are inverted.
There are two advantages of this antiperovskite family. They are metallic, so they have higher thermal conductivity than many other barocalorics, including plastic crystals. They are also chemically flexible, which means many different elements can be added to tune their properties.
The main challenge in optimizing barocalorics is reducing the hysteresis to enable potential devices to operate with minimal pressure.
Source: “Fantastic barocalorics and where to find them,” by David Boldrin, Applied Physics Letters (2021). The article can be accessed at https://doi.org/10.1063/5.0046416 .
