High performance thermoelectric nanocomposite device

#The present disclosure relates to high-efficiency thermoelectric materials, and more particularly to a thermoelectric device utilizing such materials.

#Advanced thermoelectric applications for high efficiency thermoelectric materials include solid state thermoelectric devices for converting thermal energy into electrical energy, and for cooling using electricity. Thermoelectric materials may be used in an electrical circuit between a high temperature junction and a low temperature junction. For thermoelectric power generation, a temperature difference between the junctions is utilized to generate electrical energy; while in thermoelectric cooling, electrical energy is used to transfer heat from a cold junction to a hot junction. Thermoelectric technology is of interest in many areas, including but not limited to the automotive industry, due to the potential for waste heat recovery to improve fuel economy and for environmentally friendly cooling. Significant effort has been expended to develop improved thermoelectric materials since the performance of a thermoelectric device depends, at least in part, on the thermoelectric material properties.

#The energy conversion efficiency and cooling coefficient of performance (COP) of a thermoelectric (TE) device are determined by the dimensionless TE materials' figure of merit, ZT, defined as

#Features and advantages will become apparent by reference to the following detailed description and drawings, in which like reference numerals correspond to similar, though not necessarily identical components. For the sake of brevity, reference numerals having a previously described function may not necessarily be described in connection with other drawings in which they appear.

#FIG. 1 is an enlarged, semi-schematic perspective view of an embodiment of nanowires within a controlled pore glass;

#FIG. 2 is a graphical representation depicting temperature dependence of ZT for various state-of-the-art thermoelectric materials; and

#A practical, highly efficient thermoelectric (TE) device may be formed utilizing composite materials having an overall low thermal conductivity, in addition to the TE materials (incorporated in the composite material) having desirably high thermoelectric figures of merit (ZT). A practical example of such novel composite materials is formed through use of the superior properties of thermoelectric nanowires by embedding the nanowires into templates that have the mechanical strength and desirable pore size for achieving improved thermoelectric properties of the nanowire materials. Previous attempts at forming nanocomposite TE materials used materials unsuitable for high temperature applications, or resulted in nanocomposites having an undesirably high overall thermal conductivity, with low ZT materials.

#The Seebeck effect (mentioned hereinabove) may be observed when two dissimilar materials are electrically connected to form a circuit with two junctions, maintained at different temperatures. In this arrangement, the temperature differential results in usable electrical potential, i.e., a voltage. The dissimilar materials may include an n-type and a p-type semiconductor material to make a thermoelectric generator. Recent studies have shown certain skutterudite materials to be highly efficient n-type and p-type materials for relatively high temperature thermoelectric applications. ZrNiSn-based half-Heusler alloys have shown promise as suitable n-type thermoelectric materials for high temperature applications. The ZrNiSn-based alloys and the skutterudites are candidates for use within thermoelectric generators for automotive waste heat recovery, since both classes of materials generally have optimum operation temperatures in substantially the same range as exhaust gases. In an embodiment, the temperature range of interest herein is from about 300 K to about 900 K.

#Referring now to FIG. 1, a thermoelectric nanocomposite material according to the present disclosure is designated generally at 10. The TE nanocomposite material 10 includes nanowires 12 formed from suitable, highly efficient TE materials (described further hereinbelow) having a predetermined figure of merit ZT, which figure of merit ZT is as high as possible. In an embodiment, the ZT is greater than about 1. Nanowires 12 are formed by any suitable method in a porous substrate 14 having a low thermal conductivity. Non-limitative examples of suitable methods for forming nanowires 12 in substrate 14 include vapor deposition, electrochemical deposition, and/or the like, and/or combinations thereof.