Evolution of Nanometer-Scale Microstructure within Grains and in the Intergranular Region in Thermoelectric Mg(Sb, Bi) Alloys.

n-type MgSb-MgBi alloys have been investigated as one of the most promising thermoelectric materials. To achieve high performance, a detailed understanding of the microstructure is required. Although MgSb-MgBi is usually considered to be a complete solid solution, nanosized compositional fluctuations were observed within a matrix and in the vicinity of the grain boundary.

Discovery of multivalley Fermi surface responsible for the high thermoelectric performance in YbMnSb and YbMgSb.

The Zintl phases, Yb Sb ( = Mn, Mg, Al, Zn), are now some of the highest thermoelectric efficiency p-type materials with stability above 873 K. YbMnSb gained prominence as the first p-type thermoelectric material to double the efficiency of SiGe alloy, the heritage material in radioisotope thermoelectric generators used to power NASA's deep space exploration. This study investigates the solid solution of YbMg Al Sb (0 ≤ ≤ 1), which enables a full mapping of the metal-to-semiconductor transition.

Electronic quality factor for thermoelectrics.

Development of thermoelectrics usually involves trial-and-error investigations, including time-consuming synthesis and measurements. Here, we identify the electronic quality factor for determining the maximum thermoelectric power factor, which can be conveniently estimated by a single measurement of Seebeck coefficient and electrical conductivity of only one sample, not necessarily optimized, at an arbitrary temperature. We demonstrate that thousands of experimental measurements in dozens of materials can all be described by a universal curve and a single material parameter for each class of materials.

Weighted Mobility.

Engineering semiconductor devices requires an understanding of charge carrier mobility. Typically, mobilities are estimated using Hall effect and electrical resistivity meausrements, which are are routinely performed at room temperature and below, in materials with mobilities greater than 1 cm V s . With the availability of combined Seebeck coefficient and electrical resistivity measurement systems, it is now easy to measure the weighted mobility (electron mobility weighted by the density of electronic states).

Improvement of Low-Temperature zT in a Mg Sb -Mg Bi Solid Solution via Mg-Vapor Annealing.

Materials with high zT over a wide temperature range are essential for thermoelectric applications. n-Type Mg Sb -based compounds have been shown to achieve high zT at 700 K, but their performance at low temperatures (<500 K) is compromised due to their highly resistive grain boundaries. Syntheses and optimization processes to mitigate this grain-boundary effect has been limited due to loss of Mg, which hinders a sample's n-type dopability.