Thermoelectric Materials Frank Bridges, University of California-Santa Cruz, DMR 1005568

1. Thermoelectric MaterialsFrank Bridges, University of California-Santa Cruz, DMR 1005568 The filled skutterudites LnOs4Sb12 are an important class of materials for thermoelectric applications. Several ultrasonic studies suggest that the Nd and Sm rattler atoms may be displaced significantly off center. However, EXAFS results show no evidence for the displacement of the Nd atom. The second EXAFS peak (around 3.9 Å), Nd-Os, is highly disordered even at 10K. This is not observed for Eu-Os. This suggests an unusual interaction between the Nd rattler and the Os/Sb cage. This may explain a range of other unusual effects including the softening of acoustic modes at low T. Skutterudites LnOs4Sb12 {Ln=Nd, Pr, Sm, Eu} EuOs4Sb12 Ln Os Sb NdOs4Sb12 EXAFS data were collected at T = 10 K.

2. Thermoelectric Materials Frank Bridges, University of California-Santa Cruz, DMR 1005568 Co-organized a symposium titled “Quantitative Characterization of Nanoscale Materials” at the April 2011 MRS Meeting. Graduate and undergraduate students were taught EXAFS reduction/analysis techniques. Graduate student Scott Medling presented results (left) at both a scientific conference and a materials symposium. This research explains the decreased ZT of Ba8Ga16Sn30 compared to Ba8Ga16Ge30, despite the lower thermal conductivity because the buckled cage results in an even lower electrical conductivity in Ba8Ga16Sn30. This lends understanding to how the local structure affects thermoelectric properties. Clathrates EXAFS compared to diffraction for Ba8Ga16Sn30. The different distances indicate increased cage disorder and cage buckling. M1M2M3