Liquid state properties and solidification features of the pseudo binary BaS-La₂S₃

Area of Science:

• Materials Science
• High-Temperature Chemistry
• Solid-State Chemistry

Background:

• Thermodynamic properties of barium sulfide (BaS) based chalcogenides at high temperatures are not well understood.
• Investigating pseudo-binary BaS-La2S3 systems is crucial for understanding their high-temperature behavior.

Purpose of the Study:

• To investigate the high-temperature thermodynamic properties of the pseudo-binary BaS-La2S3 system.
• To characterize the liquid phase behavior and stability of BaS-La2S3 melts.
• To determine melting points and solid-state structures within this system.

Main Methods:

• High-resolution in-situ visualization using a thermal imaging furnace.
• Containerless processing via thermal arrest measurements.
• Analysis of solidified samples to determine phase composition and density.

Main Results:

• Melting points of BaS and La2S3 were determined to be 2454 K and 2004 K, respectively.
• La2S3 exhibits high stability in its liquid state, while BaS tends to sublime.
• BaS-La2S3 melts show varying stability; La2S3-rich compositions are stable, whereas BaS-rich compositions exhibit decomposition and high vapor pressure.
• Three distinct solid solutions were identified.
• Solid and liquid densities were measured, enabling an initial estimation of the volumetric thermal expansion coefficient for La2S3.

Conclusions:

• The BaS-La2S3 system exhibits complex high-temperature behavior, with La2S3 significantly enhancing the stability of BaS.
• La2S3-rich compositions possess excellent chemical and thermal stability, making them promising for high-temperature applications.
• The study provides essential thermodynamic data and insights into the phase relationships of these technologically relevant chalcogenides.