Phase stability and property evolution of biphasic Ti–Ni–Sn alloys for use in thermoelectric applications
- Univ. of California, Santa Barbara, CA (United States). Materials Research Lab.
- Univ. of California, Santa Barbara, CA (United States)
Thermoelectric properties and phase evolution have been studied in biphasic Ti–Ni–Sn materials containing full-Heusler TiNi2Sn embedded within half-Heusler thermoelectric TiNiSn. Materials, prepared by levitation induction melting followed by annealing, were of the nominal starting composition of TiNi1+xSn, with x between 0.00 and 0.25. Phases and microstructure were determined using synchrotron X-ray diffraction and optical and electron microscopy. The full-Heusler phase is observed to be semi-coherent with the half-Heusler majority phase. Differential thermal analysis was performed to determine melting temperatures of the end-member compounds. The thermal conductivity is reduced with the introduction of a dispersed, full-Heusler phase within the half-Heusler material. This leads to an increased thermoelectric figure of merit, ZT, from 0.35 for the stoichiometric compound to 0.44 for TiNi1.15Sn. Beyond x = 0.15 ZT decreases due to a rise in thermal conductivity. Density functional theory calculations using hybrid functionals were performed to determine band alignments between the half- and full-Heusler compounds, as well as comparative energies of formation. Finally, the hybrid functional band structure of TiNiSn is presented as well.
- Research Organization:
- Energy Frontier Research Centers (EFRC) (United States). Center for Energy Efficient Materials (CEEM)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES); National Science Foundation (NSF)
- Grant/Contract Number:
- SC0001009; AC02-06CH11357
- OSTI ID:
- 1383610
- Journal Information:
- Journal of Applied Physics, Vol. 115, Issue 4; Related Information: CEEM partners with the University of California, Santa Barbara (lead); Purdue University; Los Alamos National Laboratory; National Renewable Energy Laboratory; ISSN 0021-8979
- Publisher:
- American Institute of Physics (AIP)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
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