Liquid State Properties and Solidification Features of the Pseudo Binary BaS-La2S3

Abstract

The high temperature thermodynamic properties of chalcogenides materials based on BaS remain elusive, and herein the La2S3 pseudo binary system is investigated above 1573 K. The liquid properties of BaS-La2S3 are measured by means of high resolution in-situ visualization coupled with thermal arrest measurements in a thermal imaging furnace. This enables to report for the first observation of such melts in a containerless setting. The melting points of BaS and La2S3 are revisited at 2454 K and 2004 K respectively. La2S3 demonstrates a high stability in its liquid state, in strike difference with the sublimation observed for BaS. BaS is however partially stabilized with the addition of few percents of La2S3.The remarkable chemical and thermal stability of La2S3-rich samples, contrasts with the partial decomposition and high vapor pressure observed for BaS-rich samples. Observations and analysis of the solidified samples suggests three different solid solutions. Solid and liquid densities are investigated along the different compositions, supporting a first estimate of the volumetric thermal expansion coefficient for La2S3.