Our Research

Earth Abundant Materials

The conversion efficiency of heat to electricity is generally quite low for thermoelectric materials. Therefore in order for theremoelectric generators to become a feasible option, they must be inexpensive to produce.

While many materials have broken the zT=1 barrier for thermoelectric conversion efficiency, these materials are often toxic or consist of rare/expensive elements. The research we conduct focuses on using naturally occuring or earth abundant materials to achieve high conversion efficiencies. By using naturally occuring or abundant materials, the production costs can be greatly reduced and therefore give thermoelectric generators a quicker return on investment and help to improve the efficiency of many existing systems which produce or utilize energy.

Phase Change Materials

Rewriteable data storage is, in large part, done with phase change materials. Compact discs (CD's), digital versatile discs (DVD's), and Blu-ray discs all use the strong contrast in crystalline and amorphous optical properties of phase change materials for storing data which is non-volatile and rewriteable. The phase change materials used in today's data storage originated from Dr. Ovshinky's proposal of amorphous chalcogenide semiconductors in the 1960s. In brief, these materials possess the unique ability to form an amorphous phase from a melt-quench, are stable for long periods of time, and have strong optical contrast between their amorphous and crystalline phases. Today's state-of-the-art phase change materials originate from ternary alloys of Ge, Sb, and Te.

Coincidentally, many of the materials properties necessary for adequate phase-change behavior are in-line with the requirements of efficient thermoelectric materials such as low thermal conductivity and high crystalline electrical conductivity. We are therefore studying the high temperature thermoelectric properties of Ge-Sb-Te phase change materials as potential replacements for PbTe based thermoelectric materials.

Cryogenic Materials

Solid state thermoelectric devices are desired for space-based cooling applications, such as cooling infrared sensors on satellites. Currently these sensors are cooled using mechanical cyrocooler systems. These mechanical coolers are expensive, wear out and introduce unwanted vibrations to a sensitive system. Solid-state thermoelectric (Peltier) coolers would provide a solution to many of the challenges faced in this application. Currently little work is done on thermoelectric materials in the cryogenic temperautre range, thus this research is in its nascent stages where there is still much work to be done.

This application requires new research on the fundamentals of low-temperature transport. Many rare-earth (particullarly Ce and Yb) containing compounds show suprisingly large Seebeck coefficient values in the cryogenic temperature range due to their unique electronic band structures. This unique feature is the impetus for researching novel rare-earth compounds.