Abstract
Nanostructuring approach on TiNiSn-based half-Heusler (HH) thermoelectric materials (TE) has been well established as the most prominent paradigm for achieving high figure of merit (ZT). Herein, we have extended this approach on our previously reported bulk nanocomposite (BNC), containing HH and Full Heusler (FH) with little traces of Ti6Sn5 phase in a stoichiometric composition Ti9Ni7Sn8 for the optimization of high thermoelectric performance. A synergistic effect of nanostructuring of Ti9Ni7Sn8 bulk nanocomposite (BNC) on its thermoelectric properties was noticed, revealing an enhanced value of ZT ~ 0.83 at 773 K. This enhancement in ZT value is mainly ascribed to significant reduction in thermal conductivity (κ ~ 1.0 W/mK at 773 K), through modification in grain as well as phase boundary scattering. The marginal enhancement in Seebeck coefficient observed is attributed to charge carrier filtering effect at the interface of HH/FH phases.
Highlights
Innovative developments in small-scale energy conversion technologies have gained enormous attention, especially in the utilization of low-potential heat energy
We have investigated the effect of nanostructuring of our previously reported Ti9Ni7Sn8 bulk nanocomposite (Nano-BNC) which is a composite having 97.1 ± 0.12% HH phase, 2.6 ± 0.2% in Full Heusler (FH) and traces of metallic T i6Sn5 phase for the optimization of high ZT [41]
The detail TEM investigation is performed on a Nano-BNC sample of Ti9Ni7Sn8 to investigate the minor details of microstructure of nanostructuring of bulk nanocomposite in the present work
Summary
Innovative developments in small-scale energy conversion technologies have gained enormous attention, especially in the utilization of low-potential heat energy. Comparatively low efficiency of thermoelectric materials and devices makes a wide-scale expansion of this technology economically non-profitable. In the past few years, doping, band engineering, solid solution alloying, PGEC (phonon-glass electron-crystal), nanostructuring, and spin fluctuation driven effect on electronic transport have been the prime focus for tuning thermoelectric parameters simultaneously for optimizing large ZT in different class of materials [6,7,8,9,10,11,12]. A large number of high ZT materials are either toxic or expensive which makes them irrelevant for practical use in thermoelectric generators (TEG) [13, 14]. (The practical use of several high ZT thermoelectric materials in thermoelectric generators (TEG) is difficult due to either high cost A large number of high ZT materials are either toxic or expensive which makes them irrelevant for practical use in thermoelectric generators (TEG) [13, 14]. (The practical use of several high ZT thermoelectric materials in thermoelectric generators (TEG) is difficult due to either high cost
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