Impact of Cr content on the thermoelectric properties of the Cr/Sb co-doped Mg2.2−xCrx(Si0.3Sn0.7)0.98Sb0.02 compound

The n-type Cr/Sb co-doped Mg _2.2−x Cr _x (Si _0.3 Sn _0.7 ) _0.98 Sb _0.02 (0.0025 ≤ x ≤ 0.01) compounds were successfully fabricated by applying the solid state reaction-spark plasma sintering (SPS) technique. The impact of the active Cr content on the thermoelectric properties of the co-doped compound was systematically studied. Insights from the x-ray diffraction (XRD) results indicate the existence of single-phase material of the prepared compounds. Interestingly, the lattice constant and the electrical conductivity of the samples increases with the decrease of the Seebeck coefficient as the Cr content is becomes bigger. All the fabricated compounds could achieve an excellent power factor (PF) of 3.8–4.9 mWm ^−1 K ^−2 in the range of 300–800 K. The lattice thermal conductivity declines with the increasing Cr amount. More specifically, the lowest κ _L of about 0.5 W∙m ^−1∙ K ^−1 was obtained while x = 0.01 at 650 K. The figure of merit (ZT) is also reduced by increasing the Cr content. A high ZT value of 1.4 was obtained while x = 0.0025 at 700 K.