Uranium based materials as potential thermoelectric couples for future radioisotope power systems

The actinide series possesses some of the most unique and unusual properties found anywhere in the periodic table. Unfortunately, every actinide element is radioactive to some degree, and this has made it difficult to study the fundamental properties of most actinide based materials. To date, very little work has been done to study the thermoelectric properties of materials made with actinides, and there is often disagreement in the literature that does exist. This leaves a rather large, open trade space for a facility designed to handle low-activity actinides, and process them into thermoelectric materials. Naturally occurring actinides (i.e., thorium and uranium) have a low enough activity that they can be handled with minimal safety and shielding requirements, while powdered thorium and uranium can be handled in specially prepared gloveboxes with minimal licensure requirements. This work will describe the standing-up of a laboratory, glovebox, and radiological hood designed to handle and process thorium and uranium into thermoelectric materials. Glovebox equipment includes a drill press for size reduction of large metal ingots, a high energy ball mill for blending and comminution of raw materials, an inhouse constructed hot press for processing, and a polishing station for sample preparation. All the equipment has been exercised and deemed to be ready for processing trials. Initial trials will focus on the production of La
₃
Te
₄
in order to prove the facility is capable of processing thermoelectric materials. After successful production of La
₃
Te
₄
samples, the facility will be used to produce uranium chalcogenides. These materials represent a relatively simple set of compounds that have been studied in the literature, but significant disagreement exists about the thermoelectric properties of these materials. In addition, the uranium chalcogenides can form the Th
₃
P
₄
structure, which is generally considered to be a very favorable structure for thermoelectric materials.