Giant Negative Electrocaloric Effect over an Ultra-Wide Temperature Region in Relaxation Frozen State Ferroelectrics

Area of Science:

• Materials Science
• Condensed Matter Physics
• Thermodynamics

Background:

• The electrocaloric effect (ECE) is a promising phenomenon for solid-state cooling applications.
• Existing ECE materials often have limited operating temperature ranges, hindering practical applications.

Purpose of the Study:

• To achieve a giant negative electrocaloric effect over an ultra-wide temperature region.
• To develop a strategy for extending the operational temperature range of ECE materials.
• To investigate the underlying physics of the observed phenomenon in ferroelectric films.

Main Methods:

• Utilized a relaxation frozen state ferroelectric film of Bi5Ti3AlO15.
• Employed a strategy involving gradual slowing and local freezing of relaxation dynamics.
• Applied a semiphenomenological model based on modified Ginzburg-Landau-Devonshire theory.

Main Results:

• Observed a giant negative electrocaloric effect with a temperature change range of -27.3 to -9.8 K.
• Achieved this effect over an ultra-wide temperature region of 260 K (-180 to 80 °C).
• Demonstrated that slow and frozen nanodomains lead to an inverse configuration entropy change and negative ECE.

Conclusions:

• Relaxation frozen state ferroelectrics exhibit excellent potential as electrocaloric refrigeration materials.
• The proposed strategy significantly broadens the operating temperature region for ECE.
• Breakthroughs in operating temperature and cooling change pave the way for advanced cooling technologies.