Colossal Elastocaloric Effect in Ferroelastic Ni-Mn-Ti Alloys

Area of Science:

• Materials Science
• Thermodynamics
• Solid-State Physics

Background:

• Conventional vapor-compression refrigeration is energy-intensive and environmentally impactful.
• Elastocaloric refrigeration offers an energy-efficient and eco-friendly alternative.
• High elastocaloric effects are crucial for practical elastocaloric cooling, with NiTi alloys showing the largest effects in small-scale forms.

Purpose of the Study:

• To discover and develop bulk polycrystalline materials with superior elastocaloric properties.
• To achieve a colossal elastocaloric effect exceeding that of NiTi alloys.
• To enable large-scale elastocaloric refrigeration applications.

Main Methods:

• Materials design based on achieving large volume change during phase transitions and good mechanical properties.
• Synthesis and characterization of bulk polycrystalline NiMn-based materials.
• Measurement of reversible adiabatic temperature change and isothermal entropy change.

Main Results:

• A colossal elastocaloric effect was achieved in bulk polycrystalline NiMn-based materials.
• The reversible adiabatic temperature change reached 31.5 K.
• The isothermal entropy change was as high as 45 J kg⁻¹ K⁻¹.
• These results significantly exceed the elastocaloric performance of NiTi alloys.

Conclusions:

• The developed NiMn-based materials demonstrate a colossal elastocaloric effect in bulk form, suitable for practical applications.
• This finding represents a significant advancement towards large-scale elastocaloric refrigeration.
• The materials design strategy may guide the discovery of other giant caloric effects in ferroelastic materials.