Version 2 2023-04-05, 20:10Version 2 2023-04-05, 20:10
Version 1 2023-04-03, 13:37Version 1 2023-04-03, 13:37
journal contribution
posted on 2023-04-05, 20:10authored byJoseph
Ngugi Kahiu, Samuel Kimani Kihoi, Hyunji Kim, U. Sandhya Shenoy, D. Krishna Bhat, Ho Seong Lee
The new paradigm for increasing the commercial viability
of thermoelectric
materials in the energy sector is the theoretical prediction and subsequent
experimental validation and optimization of cheaper and inherently
more efficient compositions. Herein, the experimental validation of
the recently theoretically predicted ZrFe0.50Ni0.50Sb double half-Heusler and the ability to intrinsically tune this
system to optimized p- or n-type materials by varying the Fe/Ni ratio
in the synthesized ZrFexNi1–xSb (x = 0.35–0.65) samples
are demonstrated. The samples are synthesized by arc melting, hot
pressing, and annealing. Subsequent microstructural analysis confirms
the crystallization of the ZrFexNi1–xSb into the half-Heusler structure
and reveals that the variation of the Fe/Ni ratio favors the Ni-rich
side. Consequently, the best p-type x = 0.55 and
n-type x = 0.35 samples exhibit higher power factor
values stemming from an increased carrier concentration, higher density
of state effective mass, and suppressed bipolar conduction, as indicated
by the Hall data analysis and density functional theory simulations.
The additional lattice disorders introduced by varying the Fe/Ni ratio
suppress the thermal conductivity and increase the microhardness of
the n-type samples. The ZrFe0.35Ni0.65Sb and
ZrFe0.55Ni0.45Sb samples achieve maximum zTs of ∼0.43 and 0.06, respectively, which is a great
improvement over the ∼0.001 value of the ZrFe0.50Ni0.50Sb sample. These results highlight the viability
of tuning the performance of double half-Heuslers on the doubly doped
site. They will be instrumental in demonstrating the feasibility of
developing low-cost double half-Heusler materials with better intrinsic
and highly tunable properties.