Thermoelectric properties of YbCd2Sb2 doped by Mg

• Mg alloying on the TE properties of YbCd2Sb2 is reported for the firs time.
• Useful for the thermoelectric community as YbCd2Sb2 is studied relatively few.
• By systematical Experiments, the ZT is greatly improved by 38% reaching 1.08.

p-type YbCd2-xMgxSb2 (x = 0.1, 0.2, 0.4, 0.6, 0.8) Zintl phases have been synthesized via melting reaction followed by suitable cooling, annealing, grinding, and spark plasma sintering (SPS) densification processes. The effects of isoelectronic substitution of Mg for Cd on thermoelectric properties have been investigated. Electrical conductivity, Seebeck coefficient, and thermal conductivity measurements have been performed as a function of temperature from 300 to 650 K. The XRD patterns show that the solubility limit x of Mg in the YbCd2-xMgxSb2 is less than 0.8. With increasing Mg content x, the cell parameters a and c of the YbCd2-xMgxSb2 compounds decrease. The isoelectronic substitution of Mg for Cd leads to a remarkable decrease in total thermal conductivity and an increase in Seebeck coefficient, though a slightly decease in electrical conductivity. As a result, the maximum dimensionless figure of merit ZT of 1.08 is obtained at 650 K for YbCd1.9Mg0.1Sb2. Compared with the ZT of 0.78 at 650 K in the unsubstituted YbCd2Sb2, it is improved greatly by 38%.