Thermodynamic properties of melts of the Bi–La system

DOI: 10.62564/M4-VS1425

Volodymyr Shevchuk¹, Valentina Sudavtsova¹, Natalia Podoprygora¹, Volodymyr Kudin², Larysa Romanova<sup>1

1</sup>Frantsevich Institute for Problems of Materials Science National Academy of Science of Ukraine
²Taras Shevchenko National University of Kyiv, Ukraine


Alloys and compounds of bismuth with lanthanides (Ln) exhibit thermoelectric, magnetic and other properties. For their scientifically based production, it is necessary to know both their state diagrams and the thermodynamic properties of various phases, including the liquid one, because one of the important stages of the technological processes is the melting of the initial mixtures. Thermodynamic properties of liquid solutions based on Bi of the Bi–La system were studied by the EMF method in a number of works. In this work, for the first time, the partial and integral enthalpies of the formation of melts of the Bi–La system in the entire range of compositions were determined by the method of calorimetry at 1220-1274 K. It was established that ΔHmin= −118±4 kJ/mol falls on the melt with xBi = 0.4, and =−401±23; = −212±8 kJ/mol. It has been established that ours and all known ones, except data [1], agree with each other To confirm the reliability of the obtained data and search for regularities in the thermodynamic characteristics of melts of the Bi–La system, it was considered as a member of the Bi–Ln system series. For this, the enthalpies of formation and Tmelt were analyzed of intermetallics LnBi, as well as ΔHmin of melts, relative differences of molar radii and electronegativities of components of Bi–Ln systems, based on which their dependence on the ordinal number of the lanthanide is constructed. It is shown that all dependences, except for the electronegativity differences of the components, are compatible with each other. This indicates that the thermodynamic properties of all phases of the Bi–Ln systems are determined by the size factor.

Keywords
EMF method, calorimetry, lanthanides

Acknowledgments
Not provided

References
[1] Zhang J., Sun Q, Sheng J., Electromotive force study of lanthanum in liquid bismuth, J. Molecular Liquids, 2018., 266. 229-232.