Effect of substitutions on the thermoelectric figure of merit of half-Heusler phases at 800 °C

Culp, Slade; Poon, S. J.; Hickman, Nicoleta; Tritt, Terry M.; Blumm, Jürgen

doi:10.1063/1.2168019

Cited by 234 publications

(157 citation statements)

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“…Compared with the PbTe or LAST systems, half-Heusler compounds are more environmentally benign and hence have attracted increasing levels of interest [70][71][72][73][74]. Half-Heusler compounds are crystallized in the MgAgAs-type structure with space group F4 ‾3m, which can be regarded as two interpenetrating cubic face-centered-cubic …”

Section: Half-heusler Compoundsmentioning

confidence: 99%

High-performance nanostructured thermoelectric materials

et al. 2010

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T he conversion of thermal energy to electrical energy is known as thermoelectric (TE) conversion. Th e TE eff ect can be used for both power generation and electronic refrigeration. When a temperature gradient (ΔT ) is applied to a TE couple consisting of n-type (electron-transporting) and p-type (hole-transporting) elements, the mobile charge carriers at the hot end tend to diff use to the cold end, producing an electrostatic potential (ΔV ). Th is characteristic, known as the Seebeck eff ect, where α = ΔV/ΔT is defi ned as the Seebeck coeffi cient, is the basis of TE power generation, as shown in Figure 1(a). Conversely, when a voltage is applied to a TE couple, the carriers attempt to return to the electron equilibrium that existed before the current was applied by absorbing energy at one connector and releasing it at the other, an eff ect known as the Peltier eff ect, as shown in Figure 1(b). Th ermoelectric technology and solid-state devices based on the TE eff ect have a number of advantages, including having no moving parts, and being reliable and scalable. Th e technology has therefore arouse worldwide interest in many fi elds, including waste heat recovery and solar heat utilization (power generation mode), and temperature-controlled seats, portable picnic coolers and thermal management in microprocessors (active refrigeration mode) [1].Th e effi ciency of TE devices is strongly associated with the dimensionless fi gure of merit (ZT) of TE materials, defi ned as ZT = (α 2 σ/κ)T, where σ, κ and T are the electrical resistivity, thermal conductivity and absolute temperature [2]. High electrical conductivity (corresponding to low Joule heating), a large Seebeck coeffi cient (corresponding to large potential diff erence) and low thermal conductivity (corresponding to a large temperature diff erence) are therefore necessary in order to realize high-performance TE materials. Th e ZT fi gure is also a very convenient indictor for evaluating the potential effi ciency of TE devices. In general, good TE materials have a ZT value of close to unity. However, ZT values of up to three are considered to be essential for TE energy converters that can compete on effi ciency with mechanical power generation and active refrigeration.High-performance TE materials have been pursued since Bi 2 Te 3 -based alloys were discovered in the 1960s. Until the end of last century, moderate progress had been made in the development of TE materials. Th e benchmark of ZT ≈ 1 was broken in the mid-1990s by two Tsinghua University, China Thermoelectric eff ects enable direct conversion between thermal and electrical energy and provide an alternative route for power generation and refrigeration. Over the past ten years, the exploration of high-performance thermoelectric materials has attracted great attention from both an academic research perspective and with a view to industrial applications. This review summarizes the progress that has been made in recent years in developing thermoelectric materials with a high dimensionless fi gure of...

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Section: Half-heusler Compoundsmentioning

confidence: 99%

High-performance nanostructured thermoelectric materials

et al. 2010

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“…[1][2][3][4]30 X-ray diffraction pattern for the annealed samples is shown in Figure 1. The need for long term annealing indicates large barriers for long-range atomic diffusion.…”

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Uncovering high thermoelectric figure of merit in (Hf,Zr)NiSn half-Heusler alloys

Chen

Gao

Zeng

et al. 2015

Applied Physics Letters

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Half-Heusler alloys (MgAgSb structure) are promising thermoelectric materials. RNiSn halfHeusler phases (R=Hf, Zr, Ti) are the most studied in view of thermal stability. The highest dimensionless figure of merit (ZT) obtained is ~1 in the temperature range ~450-900 o C, primarily achieved in nanostructured alloys. Through proper annealing, ZT~1.2 has been obtained in a previous ZT~1 n-type (Hf,Zr)NiSn phase without the nanostructure. There is an appreciable increase in power factor, decrease in charge carrier density, and increase in carrier mobility. The findings are attributed to improved structural order. Present approach may be applied to optimize the functional properties of Heusler-type alloys. a)

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“…In the present work, it is shown that small concentrations of vanadium substituted to the group IVB metal site of Hf 0.75 Zr 0. 25 NiSn have the effect of increasing the density of states at the Fermi level, thereby augmenting the thermoelectric properties of that compound at temperatures up to 650 K. Measurements of electrical resistivity and Seebeck coefficient were carried out simultaneously from room temperature to 1100 K on a custom apparatus that has been described previously [18] and were performed during both the heating and cooling cycles. Electrical resistivity values varied less than approximately 1% from heating to cooling cycle, while Seebeck coefficient measurements of the different cycles were consistent to within 5% of one another.…”

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confidence: 99%