Schemes for and Mechanisms of Reduction in Thermal Conductivity in Nanostructured Thermoelectrics
Nonequilibrium molecular dynamics (NEMD) simulations were performed to investigate schemes for enhancing the energy conversion efficiency of thermoelectric nanowires (NWs), including (1) roughening of the nanowire surface, (2) creating nanoparticle inclusions in the nanowires, and (3) coating the nanowire surface with other materials. The enhancement in energy conversion efficiency was inferred from the reduction in thermal conductivity of the nanowire, which was calculated by imposing a temperature gradient in the longitudinal direction. Compared to pristine nanowires, our simulation results show that the schemes proposed above lead to nanocomposite structures with considerably lower thermal conductivity (up to 82% reduction), implying ~5X enhancement in the ZT coefficient. This significant effect appears to have two origins: (1) increase in phonon-boundary scattering and (2) onset of interfacial interference. The results suggest new fundamental–yet realizable ways to improve markedly the energy conversion efficiency of nanostructured thermoelectrics.
Additional Information© 2012 American Society of Mechanical Engineers. Received 22 June 2011; revised 21 April 2012; published 6 August 2012. K.P.G. expresses his gratitude to ETH Zurich for a visiting professorship grant. X.Z. is grateful for a scholarship from the State Scholarship Fund of the China Scholarship Council that allowed him to be a visiting student at ETH Zurich and to contribute to this work. Computational support from the Brutus Cluster at ETH Zurich and Supercomputing Center of CAS in China is also gratefully acknowledged. This work was supported by a grant from the Swiss National Supercomputing Centre (CSCS) under project ID s243 and s359.
Published - JHR102402.pdf