Enhanced Thermoelectric Performance via Oxygen Manipulation in BiCuTeO
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.115
Enhanced Thermoelectric Performance via Oxygen Manipulation in BiCuTeO Hui-Ching Chang1,2,3, Hao-Jen You3, Raman Sankar4, Ying-Jay Yang1, Li-Chyong Chen2, and Kuei-Hsien Chen2,3* 1
Graduate Institute of Electronics Engineering, National Taiwan University, Taipei City 10617, Taiwan
2
Center for Condensed Matter Sciences, National Taiwan University, Taipei City 10617, Taiwan
3
Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei City 10617, Taiwan
4
Institute of Physics, Academia Sinica, Taipei, Taiwan
Abstract
BiCuTeO is a potential thermoelectric material owing to its low thermal conductivity and high carrier concentration. However, the thermoelectric performance of BiCuTeO is still below average and has much scope for improvement. In this study, we manipulated the nominal oxygen content in BiCuTeO and synthesized BiCuTeOx (x = 0.94–1.06) bulks by a solid-state reaction and pelletized them by a cold-press method. The power factor was enhanced by varying the nominal oxygen deficiency due to the increased Seebeck coefficient. The thermal conductivity was also reduced due to the decrease in lattice thermal conductivity owing to the small grain size generated by the optimal nominal oxygen content. Consequently, the ZT value was enhanced by ~11% at 523 K for stoichiometric BiCuTeO0.94 compared to BiCuTeO. Thus, optimal oxygen manipulation in BiCuTeO can enhance the thermoelectric performance. This study can be applied to developing oxides with high thermoelectric performances.
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INTRODUCTION: More than 60% of the energy from energy resources is lost as waste heat during operations; it is important to recycle this waste heat into usable energy [1]. Thermoelectric devices are a viable technology that can convert waste heat directly to electricity via a silent and clean process that does not produce CO2 gas or other wastes [2]. The performance of a thermoelectric material is characterized by ZT = (S2σ/κ)T, where (S2σ), S, σ, κ, and T are the power factor, Seebeck coefficient, electrical conductivity, total thermal conductivity, and absolute temperature, respectively [3]. The total thermal conductivity (κ) is given as κL+ κe, where κL, and κe are the lattice and electronic thermal conductivities, respectively [3]. Metal oxides are potential thermoelectric materials owing to their high thermal stability, chemical stability, and oxidization resistance [4]. BiCuTeO is a metal oxide belonging to bismuth copper oxychalcogenides, BiCuChO (Ch = S, Se, and Te), which are p-type semiconductors. Moreover, BiCuTeO exhibits better thermoelectric performance than BiCuSeO at temperatures lower than 650 K [5]. However, the state-ofthe-art dimensionless thermoelectric figure of merit (ZT) value of BiCuT
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