Extreme thermopower anisotropy and interchain transport in the quasi-one-dimensional metal Li(0.9)Mo(6)O(17)

Thermopower and electrical resistivity measurements transverse to the conducting chains of the quasi-one-dimensional metal Li(0.9)Mo(6)O(17) are reported in the temperature range 5 K = 400 K the interchain transport is determined by thermal excitation of charge carriers from a valence band ~ 0.14 eV below the Fermi level, giving rise to a large, p-type thermopower that coincides with a small, n-type thermopower along the chains. This dichotomy -- semiconductor-like in one direction and metallic in a mutually perpendicular direction -- gives rise to substantial transverse thermoelectric (TE) effects and a transverse TE figure of merit among the largest known for a single compound.Comment: PRL in press, manuscript (5pp, 4 Fig.'s) and Supplementary Material (3pp, 3 Fig.'s

Anisotropic transport in the quasi-one-dimensional semiconductor Li0.33MoO3

Transport measurements (electrical resistivity, Seebeck coefficient, and thermal conductivity) in the temperature range 80–500 K are presented for single crystals of the quasi-one-dimensional (Q1D) semiconductor Li0.33MoO3. Opposite signs are observed for the Seebeck coefficient along the trinclinic a and c axes, with Sc − Sa ≃ 250 μV/K near room temperature and ≃100 μV/K at 380 K. The thermal conductivity at room temperature in the a-c planes was ∼2 W/m K and ∼10 times smaller along b*. A weak structural anomaly at Ts  ≈ 355 K, identified in the temperature-dependent lattice constants, coincides with anomalies in the electrical properties. Analysis of the electronic transport at T > Ts favors an intrinsic semiconductor picture for transport along the most conducting Q1D axis and small-polaronic transport along the other directions, providing insight into the origin of the Seebeck anisotropy