Their calculations indicated that among the 29 missing compounds, 8 are stable. 19 investigated the thermodynamic stability of the V-IX-IV family (V = V, Nb, and Ta IX = Co, Rh, and Ir and IV = C, Si, Ge, Sn, and Pb) of half-Heuslers. 18 performed the thermodynamic analysis for 450 half-Heusler compounds and predicted that 77 are stable. Subsequently, 15 compounds were successfully synthesized to verify their prediction. 17 investigated the thermodynamic stability of 400 unreported half-Heusler compounds and 54 of them were predicted to be stable. As such, it might be beneficial to use more sophisticated theoretical studies in predicting compounds before devoting the efforts for careful experimental study. It should be noted that careful experimental synthesis and evaluation of a compound are costly, while most theoretical calculations, especially as applied in high throughput modes, are relatively inexpensive. In fact, analysis of the thermodynamic stability for the unreported compounds and assessment of potential unknown competing phases could provide highly valuable guidance for the experimental efforts. Thus, mere prediction of the thermoelectric properties for the missing compounds is not enough to guarantee experimental success. This is a particular challenge for thermoelectrics because a main approach for resolving the opposite dependencies of the transport properties, e.g., S and σ, is through unusual electronic structures, but unusual electronic properties are often found in calculations for unstable compounds, e.g., due to unfavorable bonding. A consequence of the low reliability is that the predicted compounds (especially ones that have not yet been experimentally made) with promising thermoelectric performance may be experimentally identified as metastable or unstable. Yet a key challenge is to balance the reliability and cost in such studies. This has provided the motivation for high-throughput methods and other theoretical approaches that use predictions of properties to identify candidate materials 15, 16. As a result, there is a clear need for more efficient rational approaches to discovering new promising materials. However, such a traditional process becomes increasingly time-consuming.
#Half heusler phono dispersio trial
Historically, the materials discovery has mostly relied on the Edisonian trial and error approach. In the meantime, relentless efforts have also been devoted to discovering promising new compounds that have unusual characteristics enabling favorable combinations of high electrical conductivity, large Seebeck coefficient, and low thermal conductivity. Therefore, research on thermoelectric materials has focused on identifying approaches that can effectively decouple the key transport parameters for enhancing the ZT of existing materials 9, 10, 11, 12, 13, 14. The transport parameters on which ZT depends are strongly interrelated with each other due to their different, and typically opposite, dependencies on carrier concentration and electronic structure 8. It is defined as ZT = SσT/( κ lat+ κ ele), where S is the Seebeck coefficient, σ is the electrical conductivity, κ lat is the lattice thermal conductivity, κ ele is the electronic thermal conductivity, and T is the absolute temperature 3, 4, 5, 6, 7. However, the wide application of thermoelectric power generation systems requires significant improvements in the energy conversion efficiency, which essentially depends on the materials’ dimensionless figure-of-merit ( ZT). As one of the clean energy conversion techniques, thermoelectric power generation can harvest waste heat and convert it into electricity via the Seebeck effect 1, 2. The ever-increasing energy consumption from fossil-fuel combustion has led to alarming environmental impacts. Our work demonstrates that the TaFeSb-based half-Heuslers are highly promising for thermoelectric power generation. Such an extraordinary thermoelectric performance is further verified by the heat-to-electricity conversion efficiency measurement and a high efficiency of ~11.4% is obtained. Additionally, an ultrahigh average ZT of ~0.93 between 300 and 973 K is achieved. Among them, the p-type TaFeSb-based half-Heusler demonstrates a record high ZT of ~1.52 at 973 K. By adopting this approach, here we have discovered several unreported half-Heusler compounds. Compared to the traditional materials discovery, the inverse design approach has the potential to substantially reduce the experimental efforts needed to identify promising compounds with target functionalities. However, recent progress in theoretical calculations, including the ability to predict structures of unknown phases along with their thermodynamic stability and functional properties, has enabled the so-called inverse design approach.
Discovery of thermoelectric materials has long been realized by the Edisonian trial and error approach.
0 kommentar(er)
