On the RMgSn rare earth compounds

TitleOn the RMgSn rare earth compounds
Publication TypeJournal Article
Year of Publication2009
AuthorsManfrinetti P, Provino A, Gschneidner KA
Journal TitleJournal of Alloys and Compounds
Date Published08/12
ISBN Number0925-8388
Accession NumberISI:000267891900025
Keywordscrystal structures, melting points, rare earth compounds, rare earth magnesium stannides, series, thermodynamic properties, yptas structure type

A new family of ternary rare earth compounds, RMgSn, has been synthesized and their crystal structures, formation thermodynamics and melting behavior have been studied. All of the rare earth elements (including Y) form the 1: 1: 1 equiatomic phase with Mg and Sn. These compounds crystallize with two different structure types: the RMgSn phases with the light R (R = La, Ce and Pr) adopt the orthorhombic TiNiSi structure type (an ordered derivative of the Co2Si-type structure, oP12, space group Prima), while the ones formed by the heavier R (R = Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm and Lu, plus Y) have the tetragonal CeScSi-type structure (an ordered derivative of the La2Sb-type structure, tI12, space group 14/mmm). The observed unit cell volume V-obs and the mean atomic volume V-obs/n (where n is the number of atoms in a unit cell) both decrease as expected due to the lanthanide contraction, but following different trends. The volume of formation (Delta V%) becomes more negative on going from La to Lu along the series. All phases have been found to form congruently (including YMgSn and probably LuMgSn). Their melting temperatures decrease from La to Lu, but with different slopes for the two different structure types. Relationships, between the volume of formation and also the melting points with the lanthanide contraction have been examined. The relationship between the former is anomalous compared to that observed for other RxMy series of compounds, while the latter relationship is consistent with previously published results. (C) 2009 Elsevier B.V. All rights reserved.

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