Investigation of the Na-Ga Phase Diagram

Area of Science:

• Materials Science
• Physical Chemistry
• Solid State Chemistry

Background:

• The sodium-gallium (Na-Ga) system is crucial for understanding intermetallic compound formation.
• Accurate phase diagrams are essential for predicting material properties and applications.

Purpose of the Study:

• To precisely reinvestigate the Na-Ga phase diagram.
• To determine the melting and decomposition behaviors of Na-Ga intermetallic phases.
• To characterize the liquid two-phase region and monotectic reaction.

Main Methods:

• Heat-flux differential scanning calorimetry (HF-DSC) for thermal analysis.
• Powder X-ray diffraction (PXRD) for phase identification.
• Differential thermal analysis (DTA) with a mutual sample reference method for high-resolution thermal events.

Main Results:

• The most sodium-rich phase, Na₂₂Ga₃₉, melts congruently at 549(2) °C.
• Na₇Ga₁₃, Na₂Ga₇, and NaGa₄ decompose peritectically at 545(2) °C, 501(2) °C, and 495(2) °C, respectively.
• A monotectic reaction occurs at 495(2) °C, and the critical temperature of the liquid two-phase region is estimated at 523(2) °C.

Conclusions:

• This study provides a refined Na-Ga phase diagram with precise thermal data.
• The findings clarify the complex phase equilibria and reaction pathways in the Na-Ga system.
• Accurate data on Na-Ga phase transitions are vital for materials design and processing.