Enhanced elastocaloric cooling beyond Clausius-Clapeyron limits

Area of Science:

• Materials Science
• Thermodynamics
• Solid-State Physics

Background:

• The elastocaloric effect, driven by stress-induced martensitic transformations, is a promising avenue for efficient, eco-friendly solid-state cooling.
• A key challenge is the trade-off between large entropy changes and narrow operating temperature windows in existing materials.

Purpose of the Study:

• To demonstrate an elastocaloric material overcoming the temperature span limitation for practical solid-state cooling.
• To investigate the underlying mechanisms enabling a wide operational temperature range in a novel Ti-Al-Cr alloy.

Main Methods:

• Direct measurement of elastocaloric cooling effect in a Ti-Al-Cr superelastic alloy.
• Characterization of adiabatic temperature change, cooling output, and coefficient of performance.
• Analysis of the temperature dependence of critical stress for martensitic transformation.

Main Results:

• A pronounced elastocaloric cooling effect was observed over an ultra-wide temperature range (97 K to 402 K, 305 K span).
• The material exhibited a large adiabatic temperature change (~10 K) at room temperature, with significant cooling output (5.76 J·g⁻¹) and COP (4.6).
• The elastocaloric response remained effective across the entire temperature range, mitigating the conventional trade-off between temperature span and cooling strength.

Conclusions:

• The Ti-Al-Cr alloy overcomes the inherent limitations of conventional caloric materials, offering a new regime of elastocaloric behavior.
• Anomalous temperature dependence of critical stress and high mechanical strength enable reversible transformations over a broad thermal domain.
• Findings provide a guiding principle for designing next-generation caloric materials that surpass Clausius-Clapeyron-based limitations.