Misra, D. K. and Bhardwaj, A. and Singh, Sanjay (2014) Enhanced thermoelectric performance of a new half-Heusler derivative Zr9Ni7Sn8 bulk nanocomposite: enhanced electrical conductivity and low thermal conductivity. Journal of Materials Chemistry A, 2 (30). pp. 11913-11921. ISSN 2050-7488

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Varying the valence electron concentration per unit cell (VEC) in a half-Heusler (HH) material gives a large number of structures and substructures that can be exploited to improve the thermoelectric performance. Herein, we studied Zr9Ni7Sn8 with VEC = 17.25, which is smaller than 18 for normal ZrNiSn half-Heusler, to explore the structural modifications for improvement of thermoelectric performance. The structural analysis employing XRD, SEM and TEM confirms the resulting material to be a composite of HH and Ni3Sn4-type phases. Rietveld analysis estimates the volume fraction of HH to be 75.6 +/- 1.2% and 24.6 +/- 0.8% for Ni3Sn4 phase. Interestingly, the present composite results in a substantial increase in electrical conductivity (a) by similar to 75% and a drastic reduction in thermal conductivity (x) by similar to 56%, leading to a thermoelectric figure of merit (ZT) of 0.38 at 773 K, which is similar to,85% higher than in normal HH ZrNiSn. Further, the nanostructuring of the composite, achieved by mechanical milling, derives a significantly reduced K (i.e. from 4.56 W m(-1) K-1 to 3.36 W m(-1) K-1, at 323 K), yielding a ZT of 0.90 at 773 K, which is >300% enhancement over the normal H H. The experimental results have been compared with the Bergman and Fel model for calculating effective thermoelectric parameters in composites.

Item Type: Article
Subjects: Chemistry
Energy Fuels
Materials Science
Depositing User: Dr. Rajpal Walke
Date Deposited: 01 Oct 2015 06:18
Last Modified: 01 Oct 2015 06:18
URI: http://npl.csircentral.net/id/eprint/1283

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