Thermoelectric performance of Nb-doped SrTiO3 enhanced by reduced graphene oxide and Sr deficiency cooperation
2019
Okhay, Olena | Zlotnik, Sebastian | Xie, Wenjie | Orlinski, Krzysztof | Hortiguela Gallo, Maria J. | Otero-Irurueta, Gonzalo | Fernandes, Antonio J.S. | Pawlak, Dorota A. | Weidenkaff, Anke | Tkach, Alexander
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.
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