16:15 〜 16:30
▲ [17p-F102-10] Thermoelectric properties of FeV0.955-xHf0.045TixSb half-Heusler phase
キーワード：Thermoelectric, half-Heusler
The FeVSb half-Heusler phase (HH-phase), consisting solely of cheap and non-toxic elements was studied as a new thermoelectric material. By using theoretical calculations, we found that the FeVSb HH-phase is capable of possessing a large figure of merit ZT exceeding 0.80 at a p-type condition at 700 K. To confirm this prediction, we prepared FeV1-xTixSb HH-phases alloys and found that the figure of merit ZT of FeV1-xTixSb HH-phases showed almost the same ZT-value as that predicted; ZT = 0.63 for FeV0.80Ti0.20Sb at 700 K. Notably, this value is the highest ever reported for FeVSb-based HH-phases.
The partial element substitutions, such as (Ti, Nb) for V, were reported to be an efficient way to drastically reduce the lattice thermal conductivity of FeVSb-based HH-phases. Otherwise, we realized that the influence of heavy element partial substitution such as Hf, Ta or W for V wasn’t investigated yet. In this study, therefore, we fabricated HH-phases at the compositions of FeV0.955-xHf0.045TixSb (0 < x < 0.10) to obtain a higher ZT value by decreasing the lattice thermal conductivity.
As a result, all the prepared samples contained the HH-phase as the dominant phase. We found that all the FeV0.955-xHf0.045TixSb HH-phases showed a p-type behavior at x > 0. Remarkably, the FeV0.905Hf0.045Ti0.05Sb sample exhibited a large magnitude of Seebeck coefficient exceeding 300 μV / K and a low electrical resistivity below 1.63 mΩ cm at 700 K. The lattice thermal conductivity of samples monotonically decreased with increasing Ti concentration at 0.025 < x < 0.075. The FeV0.88Hf0.045Ti0.075Sb sample showed the minimal value of 3.2 W / m K at 700 K.
Finally, the magnitude of ZT increased up to 1.15 at 700 K for FeV0.905Hf0.045Ti0.05Sb. This ZT value is almost twice than that of FeV0.80Ti0.20Sb (ZT = 0.63) previously reported.
The partial element substitutions, such as (Ti, Nb) for V, were reported to be an efficient way to drastically reduce the lattice thermal conductivity of FeVSb-based HH-phases. Otherwise, we realized that the influence of heavy element partial substitution such as Hf, Ta or W for V wasn’t investigated yet. In this study, therefore, we fabricated HH-phases at the compositions of FeV0.955-xHf0.045TixSb (0 < x < 0.10) to obtain a higher ZT value by decreasing the lattice thermal conductivity.
As a result, all the prepared samples contained the HH-phase as the dominant phase. We found that all the FeV0.955-xHf0.045TixSb HH-phases showed a p-type behavior at x > 0. Remarkably, the FeV0.905Hf0.045Ti0.05Sb sample exhibited a large magnitude of Seebeck coefficient exceeding 300 μV / K and a low electrical resistivity below 1.63 mΩ cm at 700 K. The lattice thermal conductivity of samples monotonically decreased with increasing Ti concentration at 0.025 < x < 0.075. The FeV0.88Hf0.045Ti0.075Sb sample showed the minimal value of 3.2 W / m K at 700 K.
Finally, the magnitude of ZT increased up to 1.15 at 700 K for FeV0.905Hf0.045Ti0.05Sb. This ZT value is almost twice than that of FeV0.80Ti0.20Sb (ZT = 0.63) previously reported.