Application of the Transverse Thermoelectric Effects

Abstract

Most thermoelectric applications make use of the longitudinal Seebeck and Peltier effects. However, it is possible to produce thermoelectric effects in which the electrical and thermal flows are perpendicular to one another. This has certain practical advantages; for example, it makes possible the realization of an infinite-staged cascade refrigerator using a single piece of material. The benefits of separating the directions of the electrical and thermal currents have been demonstrated convincingly at low temperatures using the transverse thermomagnetic effects, but at ordinary temperatures the transverse thermoelectric effects are of more interest. These effects are to be found in any material in which the Seebeck coefficient is anisotropic. However, for them to be of practical value, a large and strongly anisotropic Seebeck coefficient must be combined with a high ratio of electrical to thermal conductivity. There is no known homogeneous substance in which this combination of properties is to be found. On the other hand, it is possible to obtain the required parameters in a synthetic material consisting of two phases. The two components A and B should form a couple with a large conventional figure of merit Z AB . The optimum value for the transverse figure of merit Z / can approach Z AB only when the two components have very different electrical and thermal conductivities. Various workers have used semiconductor-metal or semiconductorsemimetal combinations in attempts to satisfy these requirements. It has also been proposed that the necessary combination of properties might be met by making one of the components porous. The work that has been done on synthetic transverse thermoelements will be reviewed, and the prospects for practical devices will be discussed.

Transverse Thermoelectricity in Fibrous Composite Materials

“…(3)- (5), the maximum Z trans T values were calculated for various combinations between some state-of-the-art thermoelectric materials and metals ( Table 1). As first suggested by Goldsmid when discussing lamella structures [4], a good transverse TE composite may be constructed by selecting two phases with large contrasts in their transport properties. This principle should also be applicable to fibrous composites.…”

“…The validity of this simplified mathematical model has been demonstrated by multiple studies using either finite element simulations [16,17] or experimental simplified mathematical model has been demonstrated by multiple studies using either finite element simulations [16,17] or experimental measurements [12,[18][19][20][21][22][23][24][25][26][27]. In addition to the lamella configuration, composite materials with aligned one-dimensional (1-D) inclusions, as suggested by Goldsmid [1,4], are also good candidates for transverse TE. However, there are few studies on this topic in the open literature.…”

“…In contrast, TE devices may also be constructed from elements with transverse thermoelectricity, i.e., electric current can induce a heat flow in the perpendicular direction or vice versa [3,4]. Therefore, transverse TE can potentially decouple the electric current and heat flux, and thus enable new device designs such as thin-film coolers [5,6] and cascading transverse TE devices [7,8].…”

“…In the former case, a lamella structure can be constructed from alternating layers of two materials with different TE properties, e.g., a semiconductor and a metal, and may exhibit transverse Seebeck effect in the directions neither parallel nor perpendicular to the layer planes [4].…”

OPTIMIZATION PARAMETER FOR THERMOELECTRIC PROPERTIES OF ZnO USING RESPONSE SURFACE METHODOLOGY

“…Based on the figure of merit, these materials must have the unique combination of high electrical conductivity, high Seebeck coefficient and low thermal conductivity [2]. Seebeck coefficient (S) of a material is the voltage generated between two points in the material per unit temperature difference between these points [3].…”