Complex Rare-earth Antimonide Suboxides for Thermoelectric Applications
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<p>Thermoelectric (TE) materials are able to convert heat directly into electricity and vice versa. This special property makes them valuable for a variety of applications involving power generation and refrigeration. In the search for potential high-performance TE materials, a number of rare-earth (<em>RE</em>) antimonide suboxide phases have been investigated.This presentation will focus on two classes of rare-earth antimonide suboxides: the <em>RE</em><sub>3</sub>Sb<sub>3</sub>O<sub>3</sub> and <em>RE</em><sub>8</sub>Sb<sub>3-</sub><em><sub>d</sub></em>O<sub>8</sub> phases (<em>C</em>2/<em>m</em> space group) based on the <em>RE</em>–O frameworks and the <em>anti</em>-ThCr<sub>2</sub>Si<sub>2</sub> type <em>RE</em><sub>2</sub>SbO<sub>2</sub> compounds (<em>I</em>4/<em>mmm</em> space group). The physical property measurements on the high-purity bulk samples revealed unexpected semiconducting properties in the non-charge-balanced systems, i.e.<em> RE</em><sub>8</sub>Sb<sub>3-</sub><em><sub>d</sub></em>O<sub>8</sub> and <em>RE</em><sub>2</sub>SbO<sub>2</sub>. Since the electronic structure calculations suggest that the anionic Sb states dominate the valence band at the vicinity of the Fermi level, the local structure of the Sb atomic site is believed to dictate the observed physical properties. The charge transport properties are explained within the framework of Anderson/Mott-type localizations. Ultimately, systematic investigation of the <em>RE</em><sub>2</sub>SbO<sub>2</sub> and Ho<sub>2</sub>Sb<sub>1-<em>x</em></sub>Bi<em><sub>x</sub></em>O<sub>2</sub> series reveal the large variability of the electrical properties caused by the local structural perturbations.</p>