Enhancement of thermoelectric power in layered Bi2Sr2Co2−x Ir x O y single crystals

Abstract

We report on the structural, electrical, and thermal transport properties of the single crystals of Bi2Sr2Co2−xIrxOy (0 ≤ x ≤ 0.2). Large-sized (centimeter-level) and good-quality single crystals were grown by a modified flux method. The substitution of Ir ions for Co ones makes the in-plane resistivity ρab increase monotonically, whereas, the in-plane thermopower Sab initially increases and then decreases as x is larger than 0.1. Therefore, among all samples, the in-plane power factor Pab (=Sab2/ρab) of Bi2Sr2Co1.9Ir0.1Oy would reach a maximum value of 116.4 μWm−1K−2 at 300 K and shows a significant improvement of about 20 % compared to that of the parent sample. Our results indicate that an appropriate doping of Ir ions at Co-sites may provide an effective way to enhance the thermoelectric performance of Bi2Sr2Co2Oy system.