title: High-performance tellurium-free thermoelectrics: all-scale hierarchical structuring of p-type PbSe-MSe systems (M = Ca, Sr, Ba).
abstract: We present a systematic study of the characterization and thermoelectric properties of nanostructured Na-doped PbSe embedded with 1-4% MSe (M = Ca, Sr, Ba) phases as endotaxial inclusions. The samples were powder-processed by the spark plasma sintering technique, which introduces mesoscale-structured grains. The hierarchical architectures on the atomic scale (Na and M solid solution), nanoscale (MSe nanoprecipitates), and mesoscale (grains) were confirmed by transmission electron microscopy. These structures produce a great reduction in the lattice thermal conductivity relative to pristine PbSe without appreciably affecting the power factor. The lattice thermal conductivity can be reduced by up to ∼29% when the second phase is added. The highest ZT value achieved was ∼1.3 at 923 K for both 2% SrSe-and 3% BaSe-containing samples, while the sample containing 4% CaSe showed a ZT value of ∼1.2 at 923 K. The optimal samples have hole carrier concentration of 1-2 × 10(20) cm(-3). We attribute the high ZT values to the combination of broad-based phonon scattering on multiple length scales and favorable charge transport through coherent interfaces between the PbSe matrix and MSe.
authors.affiliation: Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: Yeseul
authors.initials: Y
authors.lastname: Lee
authors.forename: Shih-Han
authors.initials: SH
authors.lastname: Lo
authors.forename: John
authors.initials: J
authors.lastname: Androulakis
authors.forename: Chun-I
authors.initials: CI
authors.lastname: Wu
authors.forename: Li-Dong
authors.initials: LD
authors.lastname: Zhao
authors.forename: Duck-Young
authors.initials: DY
authors.lastname: Chung
authors.forename: Timothy P
authors.initials: TP
authors.lastname: Hogan
authors.forename: Vinayak P
authors.initials: VP
authors.lastname: Dravid
authors.forename: Mercouri G
authors.initials: MG
authors.lastname: Kanatzidis