Thallium alloys of the rare earth: SmTI Phase diagram and molar volumes of the rare earth thallides

The SmTl system has been studied by differential thermal, metallographic and X‐ray analyses. The following intermediate phases were observed: Sm2Tl (decomposes at 1030 ± 10°C); Sm5Tl3 (decomposes at 1060 ± 10°C); SmTl (melting point, 1220 ± 20°C); Sm3Tl5 (decomposes at 940 ± 10°C); SmTl3 (melting point, 870 ± 5°C). Three eutectics occur: β‐Sm—Sm2Tl (840 ± 10°C, 18.0 ± 0.5 at % Tl); Sm3Tl5—SmTl3 (860 ± 5°C, 72.0 ± 0.5 at % Tl); SmTl3—β‐Tl (∼303°C, greater than 99.5 at % Tl); there is an eutectoidal reaction at 760 ± 10°C and 10 ± 1 at % Tl (decomposition of β‐Sm phase). Following crystal structures have been determined or confirmed: Sm2Tl hexagonal hP6—Ni2In‐type, Sm5Tl3 tetragonal tI32—W5Si3‐type, SmTl cubic cI2—W or cP2—CsCl‐type, SmTl tetragonal tP4—AuCu I‐type, Sm3Tl5 orthorhombic oC32—Pu3Pd5 like‐type, SmTl3 cubic cP4—AuCu3‐type. The characteristics of the phase diagram and the molar volumes of the SmTl compounds are compared with those of other RETl alloys and briefly discussed. Copyright © 1983 Verlag GmbH & Co. KGaA, Weinheim