Pressure Tuning of Pnicogen Chalcogenide Thermoelectrics

Open Access
Scheidemantel, Thomas John
Graduate Program:
Doctor of Philosophy
Document Type:
Date of Defense:
June 15, 2004
Committee Members:
  • Peter E Schiffer, Committee Member
  • Gerald Dennis Mahan, Committee Chair
  • John V Badding, Committee Chair
  • Jorge Osvaldo Sofo, Committee Member
  • James Bernhard Anderson, Committee Member
  • Semiconductor
  • High Pressure
  • Thermoelectricity
The thought of a cooling device or power generator with no moving parts seems almost a part of science fiction. Such devices do exist. They are used in a small niche of applications ranging from the cooling of individual solid state components to generating power aboard deep space telescopes. In this document, we present research that attempts to further improve and understand presently used and potentially new thermoelectric materials. To accomplish this we will use the well established technique of pressure tuning, along with first-principles calculations to study the effects of arsenic on currently used room temperature thermoelectric materials. The small size of arsenic may provide extra degrees of freedom in these currently used alloys. We found that pressure provides a route to the phase of As$_2$Te$_3$ that is isostructural with the rhombohedral ($Roverline{3}m$) structures of Bi$_2$Te$_3$ and Sb$_2$Te$_3$. The ambient pressure phase of As$_2$Te$_3$ is monoclinic. We also found that As$_2$Te$_3$ is more soluble in group V-VI alloys containing Sb$_2$Se$_3$ than in Bi$_2$Te$_3$ or Sb$_2$Te$_3$ alone. We also present a new host for low-dimensional thermoelectric structures. Some thermoelectric properties are enhanced by lowering the dimensionality of some materials. Current research though uses hosts and techniques that are expensive and not feasible for scaling up to commercial levels. We present a host and some techniques that may make this up-scaling a reality.