Phase equilibria, formation, crystal and electronic structure of ternary compounds in Ti–Ni–Sn and Ti–Ni–Sb ternary systems

Romaka, V.V.; Rogl, P.; Romaka, L.; Stadnyk, Yu.; Melnychenko, N.; Grytsiv, A.; Falmbigl, Matthias; Skryabina, N. E.

doi:10.1016/j.jssc.2012.08.023

Cited by 56 publications

(45 citation statements)

References 15 publications

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“…The boundaries of the two-phase field have been ascribed on the basis of the average compositions, neglecting the inhomogeneity. Nevertheless, the results, at least for the fH regions, are consistent with those of Romaka et al [25] at similar temperatures.…”

Section: Submitted To Acta Materialia (October 2015)supporting

confidence: 92%

“…The implication is that the deviations from stoichiometry are accommodated by fractional occupancy of Ni in the nominally empty sites for hH, or vacancies in the normally filled sites in fH [16,24]. While the finite width homogeneity range for the fH phase has been discussed previously in the literature [25] much less is known about the solubility range for the hH phase, although prior reports of nanoscale precipitation of fH in hH would clearly imply such solubility [7,17,26].…”

Section: (B)mentioning

confidence: 95%

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Microstructure Evolution of Biphasic TiNi1+x Sn Thermoelectric Materials

Verma

Douglas

Krämer

et al. 2016

Metall Mater Trans A

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The effects of thermal treatment on the microstructure of bi-phasic materials comprising halfHeusler (hH) and full-Heusler (fH) phases, as well as on their associated thermal conductivity, are discussed. The focus is on a biphasic hH/fH alloy of nominal stoichiometry TiNi 1.2 Sn, synthesized by containerless (magnetic levitation) induction melting. The alloy samples were exposed to various heat treatments to generate microstructures containing second phase precipitates ranging from ~10 nm to a few micrometers. The materials were characterized with regard to morphology, size, shape and orientation relationship of the fH and hH phases, both of which are present as precipitates within larger regions of the counterpart phase. The solidification path of the alloy and its implications for the subsequent microstructure evolution during heat treatment were elucidated, and relationships with the ensuing thermal conductivity were characterized.

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Section: Submitted To Acta Materialia (October 2015)supporting

confidence: 92%

Section: (B)mentioning

confidence: 95%

Microstructure Evolution of Biphasic TiNi1+x Sn Thermoelectric Materials

Verma

Douglas

Krämer

et al. 2016

Metall Mater Trans A

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“…Herein, an undoped HH derivative with generic composition Ti 9 Ni 7 Sn 8 with VEC ¼ 17.25 per formula unit which is smaller than VEC of 18 for normal TiNiSn HH has been synthesized in order to obtain any structural modifications such as either super cell structure formation of HH if possible similar to a report on Ru 9 Zn 7 Sb 8 2 or otherwise a composite phase material if phase segregation occurs for the improvement in thermoelectric performance. 1,2,31 We observed that despite to the formation of supercell of HH structure, the material exhibits a composite phase consisting of primarily HH and FH with trace amount of Ti 6 Sn 5 -type phase. Thus, this mismatch in VEC number does not allow this composition to be electronically stabilized as a supercell of HH; rather it leads to the phase separation resulting in a nanocomposite of HH TiNiSn, FH TiNi 2 Sn, and Ti 6 Sn 5 type phase.…”

mentioning

confidence: 82%

“…The half-Heusler (HH) materials with varying valence electron concentration per unit cell (VEC) results to a large number of structures and substructures that can be exploited to enhance the thermoelectric performance. [1][2][3] The HH materials which exhibit face centered cubic crystal structure [F-4 3m (no. 216)] possess a VEC of 18.…”

mentioning

confidence: 99%

“…41 It is worth mentioning that the compositional optimization in HH TiNiSn usually results in a miscibility gap in liquid, allowing a phase separation at the nano-scale, which has been well documented by several groups. 1,32,33 At high temperature, the liquid melt of Ti 9 Ni 7 Sn 8 undergoes solidification at low temperature and crystallizes to form a single solid solution of HH, FH, and Ti 6 Sn 5 phases. During cooling, this solid solution further decomposes into stable mixture consisting of HH, FH, and Ti 6 Sn 5 phases at room temperature with FH and HH being dominant phases, similar to the observation of Chai and Kimura.…”

mentioning

confidence: 99%

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Enhanced power factor and reduced thermal conductivity of a half-Heusler derivative Ti9Ni7Sn8: A bulk nanocomposite thermoelectric material

Misra

Rajput

Bhardwaj

et al. 2015

Applied Physics Letters

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We report a half-Heusler (HH) derivative Ti9Ni7Sn8 with VEC = 17.25 to investigate the structural changes for the optimization of high thermoelectric performance. The structural analysis reveals that the resulting material is a nanocomposite of HH and full-Heusler with traces of Ti6Sn5 type-phase. Interestingly, present nanocomposite exhibits a significant decrease in thermal conductivity due to phonon scattering and improvement in the power factor due to combined effect of nanoinclusion-induced electron injection and electron scattering at interfaces, leading to a boost in the ZT value to 0.32 at 773 K, which is 60% higher than its bulk counterpart HH TiNiSn.

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Unraveling Self‐Doping Effects in Thermoelectric TiNiSn Half‐Heusler Compounds by Combined Theory and High‐Throughput Experiments

Wambach

Stern

Bhattacharya

et al. 2015

Adv Elect Materials

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The control of the carrier concentration is a key topic in the optimization of the thermoelectric power factor. It depends intricately on the defect chemistry of a host phase (here: TiNiSn) and the boundary conditions set by competing phases. The large impact of a slight off‐stoichiometry in the intermetallic half‐Heusler phase TiNiSn makes combinatorial techniques ideally suited for systematic optimization of its thermoelectric performance. In this work, computational thermochemistry, combinatorial synthesis, and high‐throughput characterization are combined to obtain a complete map of the thermoelectric power factor for the Ti–Ni–Sn system. The role of the chemical potential of the constituents in determining the detailed nonstoichiometric composition of the intermetallic half‐Heusler phase TiNiSn is elucidated. This work not only confirms the assumption of a large phase‐width in terms of Ni surplus but also demonstrates that TiNiSn phases with a relatively large Ti surplus can be produced. This can serve as a new route for achieving high carrier concentrations by self‐doping in the ternary system Ti–Ni–Sn. The defect thermochemistry calculations for the carrier concentration are in excellent agreement with the experimental results. The findings of this work suggest new ways of improving the thermoelectric performance of half‐Heusler phases such as TiNiSn.

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Phase equilibria, formation, crystal and electronic structure of ternary compounds in Ti–Ni–Sn and Ti–Ni–Sb ternary systems

Cited by 56 publications

References 15 publications

Microstructure Evolution of Biphasic TiNi1+x Sn Thermoelectric Materials

Microstructure Evolution of Biphasic TiNi1+x Sn Thermoelectric Materials

Enhanced power factor and reduced thermal conductivity of a half-Heusler derivative Ti9Ni7Sn8: A bulk nanocomposite thermoelectric material

Unraveling Self‐Doping Effects in Thermoelectric TiNiSn Half‐Heusler Compounds by Combined Theory and High‐Throughput Experiments

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