The study of structural, electronic and thermoelectric properties of Ca1-xYbxZn2Sb2 (x=0, 0.25, 0.5, 0.75, 1) Zintl compounds

Based on the electronic structure, the physical properties of Ca1-xYbxZn2Sb2 (x = 0, 0.25, 0.5, 0.75, 1) Zintl compounds are studied. The transport properties can be significantly changed by varying the composition x. The materials under study are more metallic with increasing x and behaves like a semiconductor when x decreases. It is found that CaZn2Sb2 exhibits a larger thermopower magnitude (S = 241 mu V/K at T = 700 K) and the Seebeck coefficient decreases as x increases. The calculated figure of merit factor of YbZn2Sb2 is found to be low, this is explained by the fact that its structure is very compact and its bandgap is small which lead to high electrical and thermal conductivity due to high carrier concentration (n = 1:25.10(20) cm(-3) at T = 300 K). On other hand a narrow-gap (0:46 eV for CaZn2Sb2), provides a balance between a high Seebeck coefficient and low electronic thermal conductivity, with a slight increase in the carrier concentration when the temperature increases (3:87.10(19) cm(-3) at 600 K). As a consequence, CaZn2Sb2 compound is predicted to have good performance for thermoelectric applications. The electrical (sigma) and the thermal (K) conductivity for CaZn2Sb2 compound in both directions (along x and z-axes) are calculated. It is obtained that (sigma(xx)) is 120% of (sigma(zz)) at high-temperature, whereas S-zz Seebeck coefficient was higher than S-xx especially at T = 300 K (S-zz = 246 mu V/K; S-xx = 213 mu V/K). The large value of S-zz showed that the transport is dominated by zz-axis.