Google Search

A2: Medium temperature materials

Michihiro Ohta1,2, Duck Young Chung1, Masaru Kunii2, Mercouri G. Kanatzidis1,3
1Argonne National Laboratory2National Institute of Advanced Industrial Science and Technology (AIST)3Northwestern University

The thermoelectric properties of a member of the cannizzarite homologous series Pb5Bi6Se14, a member of the lillianite homologous series Pb3Bi2S6, and a member of the galenobismutite homologous series PbBi2S4 were investigated over the temperature range of 300 K to 723 K. The samples were synthesized first by melting stoichiometric amounts of the constituent elements in evacuated and sealed quartz tubes, followed by pulsed electric current sintering (SPS). The crystal structure of Pb5Bi6Se14 consists of alternating two-dimensional infinite layers of PbSe and Bi2Se3, the crystals being grown preferably with the ab-plane direction. The highly oriented texture led to highly anisotropic electrical and thermal transport properties. The crystal structures of Pb3Bi2S6 and PbBi2S4 have a three-dimensional framework assembled from Pb/Bi/S layers and strips of these layers. Therefore, the crystals were grown randomly, causing nearly isotropic electrical and thermal transport properties. All the samples showed an n-type degenerate semiconductor-like behavior with carrier concentration of 4.8 × 1019 cm−3 for Pb5Bi6Se14, 1.2 × 1019 cm−3 for Pb3Bi2S6, and 4.6 × 1019 cm−3 for PbBi2S4 at 300 K. For all the systems, the effective phonon scattering at the interfaces between layers/strips yielded the extremely low lattice thermal conductivity in the range of 0.30 W K−1 m−1 to 0.81 W K−1 m−1. The highest ZT of 0.46 at 703 K was observed in Pb5Bi6Se14 for the c-axis direction.