Syntheses, Structures, and Thermal Properties of Gyroscope-like Complexes Consisting of PtCl 2 Rotators Encased in Macrocyclic Dibridgehead Diphosphines P((CH 2 ) n ) 3 P with Extended Methylene Chains ( n = 20/22/30) and Isomers Thereof

Kharel, Sugam; Joshi, Hemant; Bhuvanesh, Nattamai; Gladysz, John A.

doi:10.1021/acs.organomet.8b00345

Abstract Eu₅Sn₂As₆is a Zintl phase crystalizing in the orthorhombic space groupPbamwith one‐dimensional chains of corner‐shared SnAs₄tetrahedra running in thec‐direction. Eu₅Sn₂As₆has an impressive room temperature Seebeck of >100 μV/K and < – 100 μV/K at 600 K crossing fromp‐ ton‐type at 650 K. The maximum thermoelectric figure of merit,zT, for Eu₅Sn₂As₆is small (0.075), comparable to that of the Zintl phase Ca₅Al₂Sb₆whose thermoelectric performance was improved by doping Na onto the Ca sites. In this study, we show that the thermoelectric properties of Eu₅Sn₂As₆can be improved by substituting with K or La. The series Eu_5‐xK_xSn₂As₆provides an increase in maximumzTof 0.22 forx=0.15 due to a decrease resistivity while the onset of bipolar conduction systematically increases in temperature. Upon La substitution, Eu_5‐xLa_xSn₂As₆results in a newn‐type Zintl phase across the temperature range of 300–800 K.

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