High temperature transport properties of BaZn₂Sn₂

BaZn₂Sn₂ (space group P4/nmm, a = 4.7459(5) Å, c = 11.330(2) Å, Z = 2) crystallizes in the CaBe₂Ge₂ structure type with a polyanionic framework comprising alternately stacked PbO-like {ZnSn_4/4} and anti-PbO-like {SnZn_4/4} layers along the c-axis. BaZn₂Sn₂ samples were obtained by either direct solid state reaction of the elements or from a Sn-flux method in very high yield with very small amount of β-Sn as the secondary phase. The samples were characterized by powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM). The chemical compositions were determined to be off-stoichiometric with Zn/Sn ratio lower than 1.0 and Sn2 atoms in the crystal structure were found to be either loosely bonded or not bonded which might lead to an incomplete charge balance. Electrical and thermal transport measurements have been performed in the temperature range 300-773 K. BaZn₂Sn₂ displays the electrical resistivity of a metal (or semimetal) along with very low Seebeck coefficients and relatively high thermal conductivity.