Optimization of thermoelectric performance in Sm-substituted SrSi₂ via carrier transport and lattice engineering

The pursuit of sustainable thermoelectric materials requires the development of cost-effective and efficient compounds derived from earth-abundant elements. Here, we investigate the effects of samarium (Sm) substitution on the thermoelectric performance of SrSi₂ with compositions Sr_1-<i>x</i>Sm_<i>x</i>Si₂ (<i>x</i> = 0, 0.05, 0.1, 0.15, and 0.2). Substituting Sm for Sr in SrSi₂ enhances the power factor at low substitution levels, while further substitution leads to a decrease, due to increased carrier scattering and reduced Seebeck coefficient. Introducing Sm substitution enhances phonon scattering through point defects, reducing lattice thermal conductivity. A peak figure of merit (<i>ZT</i>) of ~0.23 at room temperature is achieved for Sr₀.₉₅Sm₀.₀₅Si₂, demonstrating a 35% improvement over undoped SrSi₂. The weighted mobility of ~285 cm²/V·s and the tailored thermal transport emphasize the role of Sm substitution in modulating both electronic and thermal properties. These findings establish Sr_1-<i>x</i>Sm_<i>x</i>Si₂ as a promising candidate for next-generation thermoelectric devices. A high <i>p</i>-type thermoelectric power factor of 2.9 mW/K²m and <i>ZT</i> = 0.23 was achieved around room temperature by incorporating the mixed-valent Sm²⁺/Sm³⁺ ion to the earth-abundant and environmentally friendly material SrSi₂.