Lanthanum telluride ͑La 3−x Te 4 ͒ has been synthesized via mechanical alloying and characterized for thermoelectric performance. This work confirms prior reports of lanthanum telluride as a good high-temperature thermoelectric material, with zT ϳ 1.1 obtained at 1275 K. The thermoelectric performance is found to be better than that of SiGe, the current state-of-the-art high-temperature n-type thermoelectric material. Inherent selfdoping of the system allows control over carrier concentration via sample stoichiometry. Prior hightemperature syntheses were prone to solute rejection in liquid and vapor phases, which resulted in inhomogeneous chemical composition and carrier concentration. The low-temperature synthesis provides homogeneous samples with acceptable control of the stoichiometry, and thus allows a thorough examination of the transition from a heavily doped degenerate semiconductor to a nondegenerate semiconductor. The effect of carrier concentration on the Hall mobility, Seebeck coefficient, thermal and electrical conductivity, lattice thermal conductivity, and thermoelectric compatibility are examined for 0.03Յ x Յ 0.33.

Microelectromechanical systems (MEMS) are the basis of many rapidly growing technologies, because they combine miniature sensors and actuators with communications and electronics at low cost. Commercial MEMS fabrication processes are limited to silicon-based materials or two-dimensional structures. Here we show an inexpensive, electrochemical technique to build MEMS-like structures that contain several different metals and semiconductors with three-dimensional bridging structures. We demonstrate this technique by building a working microthermoelectric device. Using repeated exposure and development of multiple photoresist layers, several different metals and thermoelectric materials are fabricated in a three-dimensional structure. A device containing 126 n-type and p-type (Bi, Sb)2Te3 thermoelectric elements, 20 microm tall and 60 microm in diameter with bridging metal interconnects, was fabricated and cooling demonstrated. Such a device should be of technological importance for precise thermal control when operating as a cooler, and for portable power when operating as a micro power generator.

No abstract

Study of laser megajoule calorimeter's thermal behaviour for energy measurement uncertainty optimisation Rev. Sci. Instrum. 84, 014902 (2013) Impedance spectroscopy on ceramic materials at high temperatures, considering stray fields and electromagnetic noise Rev. Sci. Instrum. 84, 015118 (2013) An apparatus for concurrent measurement of thermoelectric material parameters Rev. Sci. Instrum. 84, 013907 (2013) Casimir probe based upon metallized high Q SiN nanomembrane resonator Rev. Sci. Instrum. 84, 015115 (2013) Four-electrode impedance spectrometer for investigation of solid ion conductors Rev. Sci. Instrum. 84, 013902 (2013) Additional information on Rev. Sci. Instrum. The implementation of the van der Pauw (VDP) technique for combined high temperature measurement of the electrical resistivity and Hall coefficient is described. The VDP method is convenient for use since it accepts sample geometries compatible with other measurements. The technique is simple to use and can be used with samples showing a broad range of shapes and physical properties, from near insulators to metals. Three instruments utilizing the VDP method for measurement of heavily doped semiconductors, such as thermoelectrics, are discussed.

No abstract