Effect of chemical pressure manipulation on the valence and thermoelectric properties of the intermediate valence compound YbCu2-xNixGe2

Gloria J. Lehr; Spencer L. Waldrop; Winston D. Carr; Donald T. Morelli

doi:10.1117/12.2228757

17 May 2016 Effect of chemical pressure manipulation on the valence and thermoelectric properties of the intermediate valence compound YbCu_2-xNi_xGe₂

Gloria J. Lehr, Spencer L. Waldrop, Winston D. Carr, Donald T. Morelli

Author Affiliations +

Proceedings Volume 9821, Tri-Technology Device Refrigeration (TTDR); 98210H (2016) https://doi.org/10.1117/12.2228757
Event: SPIE Defense + Security, 2016, Baltimore, MD, United States

Abstract

The thermoelectric properties of YbCu₂Ge₂ at low temperature are unremarkable, however it has been found to be an intermediate valence compound. Previous work has shown that manipulation of valence in such compounds by chemical pressure can have dramatic effects on the value of the Seebeck coefficient. YbCu₂Ge₂ has been found to exist in a nearly divalent, Yb²⁺, state at room temperature, which if increased towards 2.5 has the promise of increasing the Seebeck coefficient substantially. In this study a full solid solution of YbCu₂Ge₂ and YbNi₂Ge₂ was created to exert a chemical pressure on the Yb and shift the valence away from the nominally divalent. A dramatic increase in the Seebeck coefficient was found as well as a substantial decrease in the thermal conductivity. These effects resulted in a substantial increase in ZT at low temperature and further emphasized the applicability and large effect that valence manipulation can have on intermediate valence compounds.

Citation Download Citation

Gloria J. Lehr, Spencer L. Waldrop, Winston D. Carr, and Donald T. Morelli "Effect of chemical pressure manipulation on the valence and thermoelectric properties of the intermediate valence compound YbCu_2-xNi_xGe₂", Proc. SPIE 9821, Tri-Technology Device Refrigeration (TTDR), 98210H (17 May 2016); https://doi.org/10.1117/12.2228757

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