Structural Properties and Thermoelectric Performance of the Double-Filled Skutterudite (Sm,Gd)y(FexNi1-x)4Sb12

Abstract

The structural and thermoelectric properties of the filled skutterudite (Sm,Gd)y(FexNi1-x)4Sb12 were investigated and critically compared to the ones in the Sm-containing system with the aim of unravelling the effect of double filling on filling fraction and thermal conductivity. Several samples (x = 0.50–0.90 and y = 0.15–0.48) were prepared by melting-sintering, and two of them were densified by spark plasma sintering in order to study their thermoelectric features. The crystallographic study enables the recognition of the role of the filler size in ruling the filling fraction and the compositional location of the p/n crossover: It has been found that the former lowers and the latter moves toward lower x values with the reduction of the filler ionic size, as a consequence of the progressively weaker interaction of the filler with the Sb12 cavity. The analysis of thermoelectric properties indicates that, despite the Sm3+/Gd3+ small mass difference, the contemporary presence of these ions in the 2a site significantly affects the thermal conductivity of both p- and n-compositions. This occurs by reducing its value with respect to the Sm-filled compound at each temperature considered, and making the overall thermoelectric performance of the system comparable to several multi-filled (Fe, Ni)-based skutterudites described in the literature.

Investigation on the Power Factor of Skutterudite Smy(FexNi1−x)4Sb12 Thin Films: Effects of Deposition and Annealing Temperature

“…Microhardness was measured at several points of both phases on the Fe70 surface; results clearly show a clustering of data around two values, namely 462(23) and 373(14) HV, the former being associated to skutterudite and the latter to the SmSb 2 extra phase. Such a value for skutterudite is in good agreement with the values of samples belonging to the (Sm,Gd) y (Fe x Ni 1− x ) 4 Sb 12 system [ 27 ].…”

“…Data reported in Figure 10 , showing the trend of vs. temperature for both compositions of annealed films, confirm the semiconducting nature of the samples and the substantial closeness of their electrical conductivity values. A comparison with data of the (Sm,Gd) y (Fe x Ni 1− x ) 4 Sb 12 skutterudite [ 27 ] indicates that the present values are not far from the ones of dense samples with x = 0.8, while they are significantly higher than those of Sm-filled bulk samples [ 47 ].…”

“…Some examples of high-quality outcomes are the n -type (Sr,Ba,Yb)Co 4 Sb 12 with ZT ≈ 2.0 at 835 K [ 25 ] and the p -type DD 0.7 Fe 3 CoSb 12 with ZT > 1.3 at 856 K [ 26 ]. As previously mentioned, in the majority of filled skutterudite systems, both p - and n -type compounds can be synthesized from the same parent compound by tuning the filling ratio of the R atom and the partial substitution of the M atom, thus creating a lot of different compounds, such as Fe/Ni- [ 27 , 28 ] and Fe/Co- [ 29 , 30 ] based ones. At the same time, the insertion of two different M atoms, similarly to the doping by two different rare earths [ 27 ] or the partial substitution of Sb by Sn [ 31 ] or Ge [ 32 ], is responsible for the creation of additional scattering centers, and thus for a further lowering of .…”

Prospects for Electrical Performance Tuning in Ca3Co4O9 Materials by Metallic Fe and Ni Particles Additions

“…Established TE materials have ZT ≈ 1 and include PbTe, Bi 2 Te 3 , Bi 2 Se 3 [ 10 ], skutterudite [ 11 ], half-Heusler alloys [ 12 ], intermetallic Zintl phases [ 13 ], and some Si-based alloys [ 14 ]. Most of them are narrow band-gap semiconductors and have optimum performances at low and intermediate working temperature ranges.…”

Interfacial Reactivity of the Filled Skutterudite Smy(FexNi1−x)4Sb12 in Contact with Liquid In-Based Alloys and Sn

“…In this work, the wettability of the filled skutterudite Sm y (Fe x Ni 1−x ) 4 Sb 12 was studied by employing two different brazes. The cited composition was chosen due to its promising thermoelectric properties [43][44][45], as described in previous works of the present research group, where also the structural [46][47][48], mechanical [47,49] and electrochemical [50,51] features of the material were investigated. The temperature of a joint process involving Sm y (Fe x Ni 1−x ) 4 Sb 12 has to be carefully chosen since it is restricted to a limited range by the operating temperature of the thermoelectric device (the studied skutterudite system shows the maximum ZT value at~700 K) and by the peritectic decomposition temperature of the material (~873 K [52]).…”