• Calderón-Cueva, Mario
• Rylko, Megan
• Marshall, Mack
• Smiadak, David M.
• Baranets, Sviatoslav
• Bobev, Svilen
• Zevalkink, Alex

Abstract

Complex Zintl phases have yielded a large variety of promising new thermoelectric materials. In this study we report the discovery of the new Zintl phase Ca<SUB>9</SUB>(Zn<SUB>1-x</SUB>In<SUB>x</SUB>)<SUB>4</SUB>Sb<SUB>9</SUB> (x ~ 0.9), needle-like crystals of which were serendipitously obtained from an In- and Sb-rich flux. Although its composition is reminiscent of Ca<SUB>9</SUB>Zn<SUB>4+x</SUB>Sb<SUB>9</SUB>, an excellent thermoelectric material with zT &gt; 1, the substitution of In on the Zn site leads to the formation of an entirely new structure type. Single crystal X-ray diffraction revealed a structure characterized by TSb<SUB>4</SUB> tetrahedra (T = statistically disordered Zn and In atoms) and ZnSb<SUB>3</SUB> triangular units, which share common corners to form [T<SUB>4</SUB>Sb<SUB>9</SUB>]<SUP>18-</SUP> polyanions. The average structure was found to have hexagonal symmetry. The valence electron count in this heavily-disordered structure appears to follows the Zintl-Klemm rules, suggesting semiconducting behavior. Single crystal electrical conductivity and Seebeck coefficient measurements support this conclusion, suggesting that the as-grown crystals are degenerate p-type semiconductors....

Topics

• impedance spectroscopy
• single crystal X-ray diffraction
• single crystal
• phase
• electrical conductivity
• p-type semiconductor