Fast direct synthesis and compaction of phase pure thermoelectric ZnSb

Blichfeld, Anders Bank; Iversen, Bo B.

doi:10.1039/c5tc01611h

Cited by 33 publications

(27 citation statements)

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“…64,65 However, our facile, low-temperature solution-phase synthesis could be useful as a means of mitigating this problem, as it allows for reduction in grain size or nanostructuring. 13,[66][67][68][69] Characterization of LiZnSb using solid state NMR. Surface passivating ligands are a critical feature of phases prepared by low-temperature solution-phase synthesis.…”

Section: Resultsmentioning

confidence: 99%

Expanding the I–II–V Phase Space: Soft Synthesis of Polytypic Ternary and Binary Zinc Antimonides

et al. 2018

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Soft chemistry methods offer the possibility of synthesizing metastable and kinetic products that are unobtainable through thermodynamically-controlled, high-temperature reactions. A recent solution-phase exploration of Li-Zn-Sb phase space revealed a previously unknown cubic half-Heusler MgAgAs-type LiZnSb polytype. Interestingly, this new cubic phase was calculated to be the most thermodynamically stable, despite prior literature reporting only two other ternary phases (the hexagonal half-Heusler LiGaGe-type LiZnSb, and the full-Heusler Li2ZnSb). This surprising discovery, coupled with the intriguing optoelectronic and transport properties of many antimony containing Zintl phases, required a thorough exploration of syn-thetic parameters. Here, we systematically study the effects that different precursor concentrations, injection order, nucleation and growth temperatures, and reaction time have on the solution-phase synthesis of these materials. By doing so, we identify conditions that selectively yield several unique ternary (c-LiZnSb vs. h*-LiZnSb), binary (ZnSb vs. Zn8Sb7), and metallic (Zn, Sb) products. Further, we find one of the ternary phases adopts a variant of the previously observed hexagonal LiZnSb struc-ture. Our results demonstrate the utility of low temperature solution phase-soft synthesis-methods in accessing and mining a rich phase space. We anticipate that this work will motivate further exploration of multinary I-II-V compounds, as well as encourage similarly thorough investigations of related Zintl systems by solution phase methods. Disciplines Materials ChemistryComments "This document is the unedited Author's version of a Submitted Work that was subsequently accepted for publication in Chemistry of Materials, copyright © American Chemical Society after peer review. To access the final edited and published work see http://dx.doi.org/10.1021/acs.chemmater.8b02910. ABSTRACT: Soft chemistry methods offer the possibility of synthesizing metastable and kinetic products that are unobtainable through thermodynamically-controlled, high-temperature reactions. A recent solution-phase exploration of Li-Zn-Sb phase space revealed a previously unknown cubic half-Heusler MgAgAs-type LiZnSb polytype. Interestingly, this new cubic phase was calculated to be the most thermodynamically stable, despite prior literature reporting only two other ternary phases (the hexagonal half-Heusler LiGaGe-type LiZnSb, and the full-Heusler Li2ZnSb). This surprising discovery, coupled with the intriguing optoelectronic and transport properties of many antimony containing Zintl phases, required a thorough exploration of synthetic parameters. Here, we systematically study the effects that different precursor concentrations, injection order, nucleation and growth temperatures, and reaction time have on the solution-phase synthesis of these materials. By doing so, we identify conditions that selectively yield several unique ternary (c-LiZnSb vs. h*-LiZnSb), binary (ZnSb vs. Zn8Sb7), and metallic (Zn, Sb) products. Furt...

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Section: Resultsmentioning

confidence: 99%

Expanding the I–II–V Phase Space: Soft Synthesis of Polytypic Ternary and Binary Zinc Antimonides

et al. 2018

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“…Xiong et al have reported that the volume fraction of Sb phase was estimated to be ∼2wt.% by Rietveld refinement in a hotpressed sample [19] at 673K in vacuum followed by an evacuated quartz ampoule and annealed at 673K for 80h. A recent study on SPS-samples showed also that Sb phase domains were distributed along the samples, accompanied with Zn 4 Sb 3 on the surface [92]. Another difference is the final grain size of pellets.…”

Section: Thermoelectrics For Power Generation -A Look At Trends In Thmentioning

confidence: 99%

“…Considering that one of the favourable aspects of ZnSb from a commercial point of view is the low materials cost, there have been several efforts where the cost efficiency of the synthesis technique is important [92][93][94].…”

Section: Thermoelectrics For Power Generation -A Look At Trends In Thmentioning

confidence: 99%

“…The most common ones are cold-pressing (at room temperature with ultra-pressure 2-10GPa [83,91]), hot-pressing (>450°C with pressure of 20-300MPa [16,19,20,35]), and spark plasma sintering (SPS) (the electrical current is passed through the sample with 5min reaction time at 350-450°C [83,92]). One important difference among hot-presses is the manipulation of secondary phases; both removal and proportioning are possible, and obviously depends upon the temperature and duration, but also on details of the instrument design and the environment of the ZnSb powder.…”

Section: Thermoelectrics For Power Generation -A Look At Trends In Thmentioning

confidence: 99%

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Review of Research on the Thermoelectric Material ZnSb

Song¹,

Finstad²

2016

Thermoelectrics for Power Generation - A Look at Trends in the Technology

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The thermoelectric material ZnSb has been studied intensively in recent years and has shown promising features. The other zinc-antimonide compound, Zn 4 Sb 3 has remarkable low thermal conductivity, but it is accompanied with phase transitions at moderate temperature and has inherent stability problems. Compared to that, ZnSb is relatively phase stable and has a relative high charge carrier mobility and Seebeck coefficient, thus yielding a decent power factor. Meanwhile, its thermal conductivity can be reduced by means of nanostructuring, thus giving a good figure of merit at moderate temperatures, 400-600K. Many researchers have dedicated their efforts to study and improve ZnSb properties, and the figure of merit has been reported to be above one. Still, ZnSb as a thermoelectric material has features and behaviours that are not well-understood. The behaviour and properties of its intrinsic defects are not understood, but have interested researchers in recent years. This chapter intends to offer a comprehensive review on ZnSb to the readers. By combining own experiences from research on thermoelectric materials, the authors address the prospect for improving the thermoelectric properties of ZnSb and the concerns of transferring lab results to manufacturing.

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“…Further, the thermoelectric properties of bulk ZnSb are suitable for improvement by nanostructuring. 24,25 Several reports on densely packed pellets of ZnSb have appeared recently, utilizing techniques like ball-milling, [26][27][28][29][30] spark plasma sintering, 31 and cryogenic milling. 32 Optimization of doping levels and alloying elements have significantly enhanced the thermoelectric properties of ZnSb, 22,27,33,34 0021-8979/2016/119(12)/125103/10/$30.00…”

Section: Introductionmentioning

confidence: 99%

Enhancement of thermoelectric properties by energy filtering: Theoretical potential and experimental reality in nanostructured ZnSb

Berland

Song

Carvalho

et al. 2016

Journal of Applied Physics

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Energy filtering has been suggested by many authors as a means to improve thermoelectric properties. The idea is to filter away low-energy charge carriers in order to increase Seebeck coefficient without compromising electronic conductivity. This concept was investigated in the present paper for a specific material (ZnSb) by a combination of first-principles atomic-scale calculations, Boltzmann transport theory, and experimental studies of the same system. The potential of filtering in this material was first quantified, and it was as an example found that the power factor could be enhanced by an order of magnitude when the filter barrier height was 0.5 eV. Measured values of the Hall carrier concentration in bulk ZnSb were then used to calibrate the transport calculations, and nanostructured ZnSb with average grain size around 70 nm was processed to achieve filtering as suggested previously in the literature. Various scattering mechanisms were employed in the transport calculations and compared with the measured transport properties in nanostructured ZnSb as a function of temperature. Reasonable correspondence between theory and experiment could be achieved when a combination of constant lifetime scattering and energy filtering with a 0.25 eV barrier was employed. However, the difference between bulk and nanostructured samples was not sufficient to justify the introduction of an energy filtering mechanism. The reasons for this and possibilities to achieve filtering were discussed in the paper.

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Fast direct synthesis and compaction of phase pure thermoelectric ZnSb

Cited by 33 publications

References 50 publications

Expanding the I–II–V Phase Space: Soft Synthesis of Polytypic Ternary and Binary Zinc Antimonides

Expanding the I–II–V Phase Space: Soft Synthesis of Polytypic Ternary and Binary Zinc Antimonides

Review of Research on the Thermoelectric Material ZnSb

Enhancement of thermoelectric properties by energy filtering: Theoretical potential and experimental reality in nanostructured ZnSb

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