Abstract A systematic investigation pertaining to the low temperature (10–350 K) thermoelectric properties of Ni substituted Bi 1. 8− x Ni x Sb 0. 2 Te 3 alloys (x = 0–0. 08), it was synthesised employing solid state reaction method. X-ray diffraction studies verified the presence of phase pure rhombohedral structures. FESEM micrographs showed a morphological transition from hexagonal platelets to granular networks as the Ni content increased. Electrical transport measurements revealed a transition from n-type to p-type conduction for the sample x ≥ 0. 06. This transition is attributed to the formation of acceptor defects, which increases the hole concentration as a majority charge carriers. The thermal conductivity decreased systematically from 1. 7 to 1. 0 Wm −1 K −1 at 350 K with substitution of Ni concentration, as a result of the increased phonon scattering due to the mass disorder and strain fields. The optimal composition (x = 0. 04) unveiled a maximum PF and ZT of 335 μW/mK 2 and 0. 09 respectively at 350 K, ZT has 125% increment over the pristine sample. These results validates that Ni doping effectively decouples thermal and electronic transport properties via controlled defect engineering. This controlled doping represents a viable strategy for advancing thermoelectric performance of Bi–Sb–Te system.
Poojitha et al. (Mon,) studied this question.