Reduced thermal conductivity and enhanced TE performance in CrSb₂via Fe-Bi co-substitution

The efficiency of thermoelectric (TE) technology relies on the performance of TE materials. Substitution with heavy elements is an effective strategy in TE for enhancing phonon scattering without much affecting electrical transport properties. However, selecting suitable dopants to achieve a high TE figure-of-merit (ZT) poses a significant challenge. Thus, in this study, the efficacy of combined (Fe and Bi) co-substitution in CrSb₂is investigated as a promising strategy to enhance ZT by lowering thermal conductivity. A series of co-substituted Cr_1-xFe_xBi_ySb_2-y(x= 0, 0.25, 0.50, 0.75, 1 andy= 0.10, 0.15, 0.20,0.25) samples were synthesized via furnace reaction followed by spark plasma sintering technique. Phase analysis and temperature dependence TE transport properties were systematically studied on synthesized samples. Furthermore, to analyze the impact of disorder induced by Bi/Fe substitution, electronic structure calculation was performed using the projector augmented-wave method. Notably, Cr_0.75Fe_0.25Bi_0.15Sb_1.85exhibited a low thermal conductivity of ∼2.5 W m^-1K^-1at 300 K, which reduced to half compared to that of pristine CrSb₂(∼5 W m^-1K^-1). This reduction is attributed to the introduction of significant mass fluctuations and point defects along with the presence of Bi at grain boundaries by co-substitution. Consequently, a remarkable 90% enhancement inZT(∼0.021) at 350 K was achieved for Cr_0.75Fe_0.25Bi_0.15Sb_1.85compared to that of pristine CrSb₂(ZT∼ 0.012). This study can provide valuable insights into the rational design of effective dopants in other TE materials also.