Impact of Graphene Addition on the Microstructure and Thermoelectric Properties of Bi[2]Sr[2]Co[1.8]O[y] Ceramics

Abstract

The present paper reports on the impact of graphene (Gr) addition on the microstructure and thermoelectric properties of Bi[2]Sr[2]Co[1.8]O[y] ceramics. Reference and graphene added to Bi[2]Sr[2]Co[1.8]O[y]+x wt. % Gr thermoelectric (TE) materials (x=0, 0.15, 0.35, 0.70, and 1.15) were prepared by using the solid-state reaction method. The phase purity and microstructure of the samples were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. XRD analysis revealed that the addition of graphene did not alter the structure of Bi[2]Sr[2]Co[1.8]O[y] and this compound remained as a single-phase. SEM analysis showed slight increase of the amount of grains with smaller sizes for 0.35-0.70 wt. % Gr and deterioration of texturing degree for 1.15 wt. % graphene additive. Electrical transport characteristics of prepared materials were studied and values of their power factor (PF) were calculated. It was found that the incorporation of graphene into the Bi[2]Sr[2]Co[1.8]O[y] ceramics resulted in a monotonic decrease of electrical resistivity for 0.15-0.70 wt. % Gr while the Seebeck coefficient of all synthesized samples remained practically unaffected. Graphene addition leads to 1.4-fold enhancement of the power factor from 37.0 μW/(m⋅K2) at 973 K for the reference sample to 50.7 μW/(m⋅K{2}) for the sample with 0.70 wt. % Gr additive.