Enhancement in Thermoelectric Performance in Ti-doped YbCoSb Skutterudites via Carrier Optimization and Phonon Anharmonicity.

YbCoSb, being a well-studied system, has shown notably high thermoelectric performance due to the Yb filler atom-driven large concentration of charge carriers and lower value of thermal conductivity. In this work, the thermoelectric performance of YbCoTiSb (where = 0, = 0 and = 0.4, = 0, 0.04, and 0.08) upon Ti doping prepared by the melt-quenched-annealing followed by spark plasma sintering (SPS) has been studied in the temperature range of 300-700 K. Addition of Yb and doping of donor Ti at the Co site simultaneously increase the electrical conductivity to 1453.5 S/cm at 300 K, which ultimately boosts the power factor as high as ∼4.3 mW/(m·K) at 675 K in YbCoTiSb. Adversely, a significant reduction in thermal conductivity is obtained from ∼7.69 W/(m·K) (CoSb) to ∼3.50 W/(m·K) (YbCoTiSb) at ∼300 K. As a result, the maximum zT is achieved as ∼0.85 at 623 K with high hardness of 584 H for the composition of YbCoTiSb, which demonstrates it to be an efficient material suitable for intermediate temperature thermoelectric applications.