Compositionally graded Co and Cr doped TiO2 rutile for Optimum Thermoelectric Power
EMSL Project ID
14391
Abstract
Conversion of waste heat into useful energy in many applications including automobile exhausts has received considerable attention, recently. As such, there is a growing interest in synthesizing segmented thermoelements, tuned to specific temperature ranges, as thermoelectric materials over conventionally used heavy metal based materials due to its environmental friendliness. One of the main challenges facing in these materials is its poor heat to energy conversation efficiency. Concentration gradient of a dopant can be regarded as a continuously segmented thermoelement composed of a single parent material as opposed to multiple dissimilar materials. In this regard, compositional gradient is more advantageous in terms of material processing, and may result in better compatibility for device applications, especially for thin film application as gradient structures are relatively easy to produce. Recent experiments suggest that the thermoelectric parameters of oxide materials can be enhanced by controlling the “electronic spin entropy”. To this notion, we propose to develop material systems using concentration gradient of the dilute ferromagnetic spin-electric semiconducting materials (DMS), such as Co doped TiO2 in rutile phase. In the proposed work, we will investigate the fundamental scientific issues associated with growth and characterization of uniform and concentration graded of Co/Cr doped TiO2 films on Al2O3 substrates. These films will be grown in three different ways that can be distinguished by complementary abilities to control the deposit versus speed of deposition. Molecular Beam epitaxy (MBE) offers the greatest control and ability to test the material in a highly controlled fashion. Sputter deposition and ion implantation generated concentration graded Co/Cr doped rutile TiO2 films and single crystals are more commonly used in fabrication processes and will help determine the robustness and low cost fabrication possibilities. Thermoelectric properties of these samples will be measured. The ultimate goal is to develop an optimum material system for thermoelectric applications based on the knowledge and understanding developed during the proposed work. Further, we should be able to fabricate novel “unipoloar” oxide thermoelectric devices in planer configuration from this research. It is anticipated that the outcome of this project will not only impact the thermoelectric research at PNNL and UW, but also help several other technological areas including gas sensors, optoelectronics and photonics area and help to establish a strong joint program between PNNL and UW in this area.
Project Details
Project type
Exploratory Research
Start Date
2005-03-20
End Date
2007-03-22
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
A. Yamamoto, V. Shutthanandan2, L. Saraf, S. Thevuthasan, F.S.Ohuchi. "Thermoelectric Properties of Ni implanted TiOx thin film
with graded dose structure", 25th International Conference on Thermoelectrics, Aug.8,2006, Wien (POSTER)