Effects of Ge substitution on thermoelectric properties of CrSi 2

Polycrystalline Cr(Si 1− x Ge x ) 2 samples were prepared using arc melting and spark plasma sintering methods. Single-phase Cr(Si 1− x Ge x ) 2 samples were obtained for the compositional range of 0 ≤ x ≤ 0.015 and the lattice parameters monotonically increased with x . In the range of single phases, the electrical conductivity and Seebeck coefficient increased and decreased with increasing x , respectively. The partial substitution of Ge effectively reduced the thermal conductivity to ∼80%, which resulted in the increase in the ZT of Cr(Si 1− x Ge x ) 2 samples from 0.16 ( x = 0) to 0.25 ( x = 0.015) at 600 K. From the results of first-principles calculation for transport properties, it can be concluded that the origin of the increase in electrical conductivity and the decrease in Seebeck coefficient of Ge-substituted samples is the decrease in carrier effective mass.