Formation and Decomposition Process of the Filled Skutterudite Smy(FexNi1-x)4Sb12(0.40 <= x <= 1) as Revealed by Differential Thermal Analysis

Filled skutterudites are among the most promising thermoelectric materials, and the obtainment of monophasic samples is crucial for the study of their transport properties. In this work, a differential thermal analysis study was performed on samples belonging to the Smy(FexNi1-x)4Sb12 system with the aim to determine the most proper annealing temperature to possibly obtain skutterudite monophasic samples, and to study the effect of Sm addition on the thermodynamics of the Fe-Ni-Sb system. Samples were prepared through the traditional procedure consisting in melting-quenching-annealing the starting elements. DTA analyses were carried out on annealed samples, and results were interpreted using the Fe25Sb75-Ni25Sb75 pseudobinary phase diagram taken from the literature as a starting point. They reveal that 870 K is the best annealing temperature, being the formation of a liquid phase just above this point; moreover, the Sm introduction results in widening the one-phase skutterudite stability region toward both higher temperatures and higher Fe concentrations compared with the Sm-free system.