Expression of interfacial Seebeck coefficient through grain boundary engineering with multi-layer graphene nanoplatelets
Artikel i vetenskaplig tidskrift, 2020

Energy filtering has been a long-sought strategy to enhance a thermoelectric material's figure of merit zT through improving its power factor. Here we show a composite of multi-layer graphene nanoplatelets (GNP) and n-type Mg3Sb2 leads to the expression of an energy filtering like effect demonstrated by an increase in the material's Seebeck coefficient and maximum power factor, without impact on the material's carrier concentration. We analyse these findings from the perspective of a heterogeneous material consisting of grain and grain boundary phases, instead of a more traditional and common analysis that assumes a homogeneously transporting medium. An important implication of this treatment is that it leads to the development of an interfacial Seebeck coefficient term, which can explain the observed increase in the material's Seebeck coefficient. The contribution of this interfacial Seebeck coefficient to the overall Seebeck coefficient is determined by the relative temperature drop across the grain boundary region compared to that of the bulk material. In Te doped Mg3Sb2 we show the introduction of GNP increases the interfacial thermal resistance of grain boundaries, enhancing the contribution of the interfacial Seebeck coefficient arising from grain boundaries to the overall Seebeck coefficient. Without significant detriment to the electrical conductivity this effect results in a net increase in maximum power factor. This increased interfacial thermal resistance also leads to the synergistic reduction of the total thermal conductivity. As a result, we enhance zT of the Mg3Sb2 to a peak value of 1.7 near 750 K. Considering the two-dimensional nature of the grain boundary interface, this grain boundary engineering strategy could be applied to a few thermoelectric systems utilizing various two-dimensional nanomaterials.

Författare

Yue Lin

Northwestern University

University of Cambridge

Maxwell Wood

Northwestern University

Kazuki Imasato

Northwestern University

Jimmy Jiahong Kuo

Northwestern University

David Lam

Northwestern University

Anna Nooshin Mortazavi

Monash University

Harvard University

Tyler J. Slade

Northwestern University

Stephen A. Hodge

Versarien

Kai Xi

University of Cambridge

Mercouri G. Kanatzidis

Northwestern University

David R. Clarke

Harvard University

Mark C. Hersam

Northwestern University

G. Jeffrey Snyder

Northwestern University

Energy & Environmental Science

Vol. 13 4114-4121

Ämneskategorier

Keramteknik

Materialkemi

Den kondenserade materiens fysik

DOI

10.1039/D0EE02490B

Mer information

Skapat

2020-11-12