Nanostructuring in β-Zn_4Sb_3 with variable starting Zn compositions
Thermoelectric Zn_(4−δ)Sb_3 samples with varying Zn concentrations were synthesized. The morphology, along with planar and extended defects was studied using transmission electron microscopy (TEM). For all the Zn concentrations, nanostructuring was observed. Depending on the Zn concentration, two different types of nanostructures were observed: nanovoids and nanograins. Three samples with Zn:Sb ratios of 1.28, 1.30, and 1.36 were studied. The presence of the secondary phases was discussed in terms of the phase diagram. Density functional theory (DFT) calculations further elucidated the formation of secondary phases as a function of different Zn:Sb ratio.