ICT2014 Abstracts

Since the 1960s, the state-of-the-art thermoelectric power system for space applications has typically been based up on either SiGe alloys or PbTe/TAGS. Although reliable and robust, the thermoelectric performance of these systems remains fairly low with a conversion efficiency of ~6%. In recent years, complex materials such as n-type La_3-xTe₄ and p-type Yb₁₄MnSb₁₁ have emerged as new high efficiency, high temperature thermoelectric materials with ZTmax on the order of 1.2 at 1275 K. The high performance of these complex structures is attributed to their favorable characteristics such as: semi-metallic behavior due to small band gaps, low glass-like lattice thermal conductivity values due to structural complexity and reasonably large thermopower values near their peak operating temperatures. Current efforts  at JPL are focused at achieving higher thermoelectric conversion efficiencies, in excess of 20%, in the next few years. The research areas include examining other structurally complex refractory compounds, engineering of composite materials to decouple and optimize electrical and thermal transport properties and compositional tuning guided by computationally intensive first principles theoretical calculations.We will present an overview of recent research efforts at JPL and collaborating institutions on these systems and will discuss approaches and preliminary results on the properties of these rare earth compounds and their impact to ZT.