Rare earth metal‐doped Zintl phase thermoelectric materials: The Yb_5−xRE_xAl₂Sb₆ (RE=Pr, Nd, Sm) system

Abstract

Three Zintl phase solid solutions in the Yb 5 À x RE x Al 2 Sb 6 (RE = Pr, Nd, Sm) system have successfully been synthesized by arc melting followed by annealing. The isotypic crystal structure of these compounds was characterized by PXRD and SXRD analyses, and their Ca 5 Al 2 Bi 6 -type structure (space group Pbam, Z = 2) was described as a combination of (1) the 3-dimensional anionic [Al 2 (Sb 4 Sb 4/2 )] frameworks and (2) the space-filling cations Yb 2+ and RE 3+ located in between the anionic frameworks. In particular, the anionic frameworks were originally built from the two neighboring tetrahedral [AlSb 4 ] moieties via the Sb1-Sb1 bridges. The site-preference of RE 3+ for the Yb3/RE-site with the mixed occupation ratio between ca. 9% and 16% of RE 3+ was elucidated by the size-factor criterion based on the size match between the cationic size and the site volume. The band structures, density of states, and crystal orbital Hamilton population curve analyses were conducted by the tightbinding linear muffin-tin orbital method, and the results proved that the RE 3+doping increased the band degeneracies and the number of resonance peaks near the Fermi level resulting in the improved Seebeck coefficients. The electrical transport property measurements proved that despite the successful addition of n-type RE 3+ dopants in the title Yb 5 À x RE x Al 2 Sb 6 system, the electrical conductivity decreased due to the canceling off of the newly added n-type carriers by the already existing p-type carriers resulting in still the p-type character. However, the enhanced Seebeck coefficients predicted by the increased effective mass from the DFT calculations eventually improved the overall power factor of the RE 3+ -doped title compounds.

SnSe: The rise of the ultrahigh thermoelectric performance material

“…4,5 TE power generators are electronic devices consisting of n-and p-type semiconductors, and can directly transform thermal into electric energy. [6][7][8][9][10][11] The temperature difference subject to the material induces the potential difference by virtue of the Seebeck effect, thereby generating electric current spontaneously. This feature gives unique advantages of the TE power generation.…”

“…Thermoelectric (TE) technology can simultaneously contribute to solving such energy and environmental problems 4,5 . TE power generators are electronic devices consisting of n‐ and p‐type semiconductors, and can directly transform thermal into electric energy 6–11 . The temperature difference subject to the material induces the potential difference by virtue of the Seebeck effect, thereby generating electric current spontaneously.…”