Vaporisation thermodynamic studies over and biphasic regions of U-Sn system using high temperature mass spectrometry

Abstract

High-temperature vaporisation thermodynamic studies over <U3Sn7(cr) + USn2(cr)> and <USn2(cr) + USn(cr)> two-phase regions were carried out by employing Knudsen Effusion Mass Spectrometry (KEMS) in the temperature range 1148–1465 and 1222–1471 K, respectively. Sn(g) was the only species observed in the mass spectra of the equilibrium vapour phase over both the biphasic regions. The partial pressure-temperature relations of Sn(g) were deduced aslog(pSn/Pa) = (−15,737 ± 73)/(T/K)) + (9.52 ± 0.06) (1148–1465 K) <U3Sn7(cr) + USn2(cr)> andlog(pSn/Pa) = (−16,151 ± 67)/(T/K)) + (9.70 ± 0.05) (1222–1471 K) <USn2(cr) + USn(cr)>Using p-T relations, the enthalpies of the following heterogeneous reaction equilibria were evaluated by the second law method: U3Sn7(cr) = 3USn2(cr) + Sn(g) and USn2(cr) = USn(cr) + Sn(g). Subsequently, the Gibbs energies of the formation of U3Sn7(cr) and USn2(cr) were derived. Knudsen effusion mass spectrometric studies over these two biphasic regions are being reported for the first time.