Enhanced rectification effect in silver chalcogenide-based thermal diode by using precipitation/dissolution of Ag...

Area of Science:

• Materials Science
• Solid-State Physics
• Nanotechnology

Background:

• Developing high-performance composite-type thermal diodes is crucial for advanced thermal management.
• Silver chalcogenides exhibit structural phase transitions between 350 K and 473 K, causing significant changes in thermal conductivity.
• Understanding composition-dependent thermal properties across phase transitions is key for material design.

Purpose of the Study:

• To investigate the composition dependence of thermal conductivity in silver chalcogenides (Ag$_{2+x}$Te$_{0.9}$S$_{0.1}$ and Ag$_{2}$S$_{1-y}$Se$_{y}$) across their phase transitions.
• To explore the potential of these materials for creating high-performance composite thermal diodes.
• To achieve enhanced thermal rectification through controlled phase transitions and material composition.

Main Methods:

• Synthesis of Ag$_{2+x}$Te$_{0.9}$S$_{0.1}$ and Ag$_{2}$S$_{1-y}$Se$_{y}$ samples with precisely controlled compositions.
• Measurement of temperature-dependent thermal conductivity across the phase transition.
• Fabrication of a composite thermal diode using optimized Ag$_{2.025}$Te$_{0.9}$S$_{0.1}$ and Ag$_{2}$S$_{0.6}$Se$_{0.4}$ compositions.

Main Results:

• Ag$_{2}$Te$_{0.9}$S$_{0.1}$ showed a stepwise decrease in thermal conductivity upon transitioning to the high-temperature phase (HTP), enhanced by excess silver (up to 2.7-fold change).
• Ag$_{2}$S$_{1-y}$Se$_{y}$ exhibited a stepwise increase in thermal conductivity from the low-temperature phase (LTP) to HTP (up to 5-fold change at y=0.4).
• A composite thermal diode achieved a thermal rectification ratio (TRR) of 3.3, the highest reported for all-solid-state devices.

Conclusions:

• Silver chalcogenides with tailored compositions can exhibit significant, opposing changes in thermal conductivity during phase transitions.
• The controlled dissolution and precipitation of silver in Ag$_{2+x}$Te$_{0.9}$S$_{0.1}$ effectively modulates thermal conductivity.
• The fabricated composite thermal diode demonstrates the potential of these materials for highly efficient, solid-state thermal management applications.