Thermoelectric performance of Nb-doped SrTiO3 enhanced by reduced graphene oxide and Sr deficiency cooperation

Oxide materials are of current interest as high-temperature thermoelectrics in the automotive and manufacturing energy-harvesting sectors due to high chemical robustness, low toxicity and low cost. Driven by a need to improve the thermoelectric performance of n-type oxides to the level of p-type analogues, ceramics and composites based on donor-doped SrTiO3 are considered as a promising material. Here Nb-doped SrTiO3 with Nb content of 10 and 15% as well as Sr/(Nb + Ti) ratio of 1.00 and 0.98 was mixed with 0.6 wt. % of graphene oxide (GO) prepared by Hummer-based method and conventionally sintered in atmosphere of H2/N2 to reduce both Nb-doped SrTiO3 and GO. Addition of reduced GO in combination with introduction of Sr vacancies provides a synergistic effect of fastening charge transport and thereby increasing electrical conductivity σ and suppressing the thermal conductivity κ. These factors, together with a moderate Seebeck coefficient S, result in a high power factor PF = S2 × σ up to ∼1.98 mW/(K2m) and thermoelectric figure of merit ZT = PF × T/κ up to 0.29. These findings offer further prospects for seeking high performance SrTiO3-based thermoelectrics by modification with reduced GO.