Thermoelectric Properties of Mixed-Metal Tellurides
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1044-U08-04
Thermoelectric Properties of Mixed-Metal Tellurides Anthony V Powell1, Fabien Guinet1, Paz Vaqueiro1, Ian M Wilcock2, and Richard L Jones2 1 Department of Chemistry, Heriot-Watt University, Riccarton, Edinburgh, EH14 4AS, United Kingdom 2 Physical Sciences Department, DSTL, Salisbury, SP4 0JQ, United Kingdom ABSTRACT A new series of thallium-containing materials, Tl1-xPbmATe m+2 (A= Sb, Bi; m=10, 18; 0≤x≤0.3), has been prepared. Diffraction data reveal that a rocksalt-type structure is adopted at all compositions. Transport property measurements indicate n-type behaviour for the bismuthcontaining materials and p-type for the antimony analogues. The reduced power factors for the latter, compared to the bismuth-containing materials, are primarily due to their more resistive nature. The highest power factors occur at a thallium deficiency in the range 0.1≤x≤0.2. Measured thermal conductivities are reduced from that of the binary telluride, suggesting that the materials may have potential as n/p-type components in device applications.
INTRODUCTION Thermoelectric materials offer a unique opportunity for the construction of devices for cooling and power generation that possess significant advantages over conventional technologies. However, the provision of materials suitable for fabrication of high-efficiency devices remains a major scientific challenge. The thermoelectric performance of a material is dependent on an unusual combination of high electrical conductivity (σ), typically found in metals, together with a low thermal conductivity (κ) and high Seebeck coefficient (S), characteristics more usually associated with non-metallic systems, and is embodied in the dimensionless figure of merit, ZT = S2σT/κ. There has been a recent resurgence of interest in the development of new thermoelectric materials with ZT values that exceed one. In particular, attempts to reduce the lattice contribution to the thermal conductivity, without impairing the electrical transport properties, have exploited the concept of a phonon-glass-electron-crystal proposed by Slack [1]. This has entailed synthesis of materials containing weakly-bound species whose localised vibrational modes serve to scatter heat-carrying phonons [2]. Alternative approaches have stemmed from theoretical work by Hicks and Dresselhaus [3] who suggested that confinement of electron transport in a two-dimensional quantum well enhances the density of states which, together with a reduction in the phonon mean-free path, could lead to increases in ZT. This has stimulated considerable efforts to achieve experimental realization of such predictions in thin-film superlattices [4,5,6]. Recently, a family of materials of general formula AgPbmSbTe m+2 has been shown to exhibit excellent thermoelectric properties in the bulk phase at elevated temperatures [7]. Although nominally a solid solution between PbTe and the ternary phase AgSbTe2, careful investigation [8,9] has shown that these materials exhibit (Ag, Sb)-rich regions within a PbTe matrix, leading to the for
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