Enhanced High-Temperature Thermoelectric Performance of Yb₄Sb₃ via Ce/Bi Co-doping and Metallic Contact Deposition for Device Integration

Abstract

Thermoelectrics (TE) for very high temperatures (>800 K) have numerous potential applications in heavy industry and space exploration. This article focuses on the compound Yb4Sb3 which is a promising p-type counterpart to the structurally related and high-performance n-type RE3Te4 (RE = Nd, La, Pr) for the fabrication of high-temperature TE modules. A quick and efficient method for synthesizing pure and fully dense Yb4Sb3 samples was developed and optimized using high-energy ball milling followed by reactive spark plasma sintering. The technique was utilized to produce a series of doubly doped Ce x Yb4–x Bi0.2Sb2.8 compounds. X-ray diffraction and scanning electron microscopy (SEM) were employed to establish the solubility limit of Ce, which was determined to be x = 0.4. TE properties of Yb4Sb3 and Ce0.4Yb3.6Bi0.2Sb2.8 were measured up to 1273 K, revealing that the doping strategy was effective in reducing the charge carrier concentration and thermal conductivity. This led to a significant increase in the TE figure-of-merit zT from 0.2 to 0.4 at 1273 K. In addition, screening of metallic contacts was conducted for the development of a thermoelectric module with Yb4Sb3. The results showed that two robust TE legs with Ni and Cu contacts were successfully produced through spark plasma sintering. The measured electric contact resistances were very promising, with average values of 2 and 1 μΩ cm2 for Ni and Cu contacts, respectively.

Advancing very high temperature thermoelectric performance of Yb4Sb3 through dual-substitutions: a combined experimental and theoretical study

“…However, compositions with x ≤ 0.3 display no LaSb impurities and exhibit undistorted peaks, signifying successful substitution of La and Bi for Yb and Sb, respectively, in the structure. This solubility limit is slightly lower than that observed in the Ce-inserted Ce x Yb 4− x Sb 2.8 Bi 0.2 solid solution ( x = 0.5), 22 mainly owing to the higher atomic radius of La atoms (1.95 Å) compared with Ce atoms (1.85 Å). The refined cell parameters are displayed in Fig.…”

“…Very recently, we used a similar strategy with partial Bi substitution on Sb sites while a partial amount of Yb atoms were replaced by Ce atoms. 22 Findings from this study demonstrated a significant enhancement in the thermoelectric properties of the Ce-substituted solid solution, motivating further exploration into the transport properties of the La-substituted solid solution.…”

“…This occurrence is in line with a recent research work demonstrating the rapid surface oxidation of the related Yb 14 MnSb 11 compound around 700 K, 32 and was also pointed out in our recent study on the Ce x Yb 4− x Sb 2.8 Bi 0.2 solid solution. 22 Although these factors contributed to certain limitations in achieving precise measurements, in particular for the La 0.3 Yb 3.7 Sb 2.8 Bi 0.2 composition which will not be presented here, the measurements of the binary Yb 4 Sb 3 and La x Yb 4− x Sb 2.8 Bi 0.2 ( x = 0.1 and 0.2) compounds were reasonably successful and allowed us to gain valuable insights into the influence of the present dual substitution on the transport properties.…”