Liquid state properties and solidification features of the pseudo binary BaS-La(2)S(3)

The high temperature thermodynamic properties of chalcogenides materials based on BaS remain elusive. Herein the pseudo binary BaS-La(2)S(3) is investigated above 1573 K. The liquid properties of BaS-La(2)S(3) are measured by means of high resolution in-situ visualization coupled with thermal arrest measurements in a thermal imaging furnace. This enables to report the first observation of such melts in a container-less setting. The melting points of BaS and La(2)S(3) are revisited at 2454 K and 2004 K respectively. La(2)S(3) 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 La(2)S(3). The remarkable chemical and thermal stability of La(2)S(3)-rich samples contrasts with the partial decomposition and high vapor pressure observed for BaS-rich samples. Observations and analysis of the solidified samples suggest 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 La(2)S(3).