THERMAL-ANALYSIS OF PSEUDO-BINARY SYSTEM - LICL-KCL EUTECTIC AND LANTHANIDE TRICHLORIDE

The phase diagrams of the pseudo-binary systems of LiCl-KCl eutectic a nd lanthanide trichloride (LnCl(3): Ln = La, Ce, Pr, Nd, Sm, and Gd) w ere determined for compositions less than 25 mol% LnCl(3) by means of thermal analysis, visual observation, electromotive force measurement and powder X-ray diffraction. The existence of K(2)LnCl(5) compounds w as confirmed in all the systems, but K(3)LnCl(6) was observed only in the systems containing Sm and Gd. In the region up to 17 mol% LnCl(3), the eutectic temperature and composition were observed to be close to those of the LiCl-KCl eutectic system (625 +/- 1 K, LiCl-41 at.% KCl) . For compositions greater than 17 mol% LnCl(3), on the other hand, th e eutectic points were 701 +/- 1, 691 +/- 1, 681 +/- 1, 656 +/- 1, 635 +/- 1 and 649 +/- 1 K for La, Ce, Pr, Nd, Sm, and Gd, respectively. T he liquidus surface of the LiCl-KCl-LaCl3 system was also determined a t compositions up to 40 mol% LnCl(3). (C) 1997 Elsevier Science B.V.