Nanocomposites and nanomaterials

Thermoelectric Nb doped SrTiO3 with reduced graphene oxide
Okhay O.1, Hortiguela-Gallo M.1, Otero-Irurueta G.1, Zlotnik S.2, 
Orlinski K.2, Pawlak D.A.2, Xie W.3, Weidenkaff A.3, Tkach A.4
1 TEMA, Department of Mechanical Engineering, University of Aveiro, 3810-193, Aveiro, Portugal. 
E-mail: olena@ua.pt
2 Institute of Electronic Materials Technology (ITME), Warsaw, Poland.
3 Institute for Materials Science, University of Stuttgart, 70569 Stuttgart, Germany.
4 CICECO – Aveiro Institute of Materials, Department of Materials and Ceramic Engineering, University of Aveiro, 3810-193, Aveiro, Portugal.

New power generation strategies are needed for clean and sustainable energy sources due to exponentially rising energy demands of the word. Thermoelectric (TE) conversion of widely distributed waste heat was proposed as an alternative route to convert thermal or solar energy into electric power economically. Oxide materials are of current interest as high-temperature TEs in the energy-harvesting sectors due to high chemical robustness, low toxicity and low cost although their TE figure of merit ZT is lower than that of chalcogenides or skutterudites [1]. Driven by a need to improve TE performance of n-type oxides, ceramics and composites based on donor-doped SrTiO3 are considered as a promising material.
Within this context, Nb-doped SrTiO3 is mixed with graphene oxide (GO) and conventionally sintered in atmosphere of H2/N2 to reduce both Nb-doped SrTiO3 and GO. Addition of reduced GO (rGO) in combination with introduction of Sr vacancies provides a synergistic effect of fastening charge transport and thereby increasing electrical conductivity and suppressing the thermal conductivity. These factors, together with a moderate Seebeck coefficient, result in a high power factor PF ∼1.98 mW/(K2m) and ZT up to 0.29 [2]. Such findings offer further prospects for seeking high performance SrTiO3-based TEs by modification with rGO. Deep comparison with other thermoelectric composites with rGO is done.

1.	O. Okhay, A. Tkach, Impact of Graphene or Reduced Graphene Oxide on Performance of Thermoelectric Composites // C.-2021.-7.-37.
2.	O. Okhay et al., Thermoelectric performance of Nb-doped SrTiO3 enhanced by reduced graphene oxide and Sr deficiency cooperation, Carbon.-2019.-143.-215-222.