EXAFS study of thermoelectric BiCuOSe: Effects of Cu vacancies

Chou, Tsung-Lin; Tewari, Girish C.; Chan, Ting‐Shan; Hsu, Yao Jane; Yamauchi, H.; Karppinen, Maarit

doi:10.1016/j.ssc.2015.01.007

Cited by 13 publications

(5 citation statements)

References 28 publications

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“…In addition, the material was confirmed to be Ag-deficient [0.94(1) per formula]. For comparison, the occupancies of the other atoms sites were found to be 1.000 (3) for Bi, 1.003 (8) for S, and 1.00 (1) for O during independent refinements, thus allowing us to reach a conclusion in the absence of deficiencies in these regular sites. The conventional reliability factors converged to the following values: R p = 0.032, R wp = 0.043, R Bragg = 0.023, and χ 2 = 3.9; the residual electron densities on Ag sites were 0.6 e Å −3 on Ag1 and −0.3 e Å −3 on Ag2, and the extreme values were 1.6 and −0.8 e Å −3 , respectively, in and around the Bi site (see also Figure 2b for the final Rietveld plot and Table 1 for the crystallographic data).…”

Section: Bicuos Ag Biagos Cumentioning

confidence: 93%

“…The structure consists of alternating layers of (Bi 2 O 2 ) 2+ and (Cu 2 Ch 2 ) 2– . BiCuOCh phases have been widely studied for their thermoelectric properties, − owing to their intrinsically low thermal conductivity as well as their high electronic conductivity. Indeed, they are naturally degenerated p-type semiconductors with low bandgap values (from 0.4 eV for BiCuOTe to 1.1 eV for BiCuOS). , Among these compounds, Ba-doped BiCuOSe exhibits the best reported figure of merit ( ZT = 1.4 at 923 K) …”

Section: Introductionmentioning

confidence: 99%

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Substituting Copper with Silver in the BiMOCh Layered Compounds (M = Cu or Ag; Ch = S, Se, or Te): Crystal, Electronic Structure, and Optoelectronic Properties

et al. 2018

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The synthesis of BiAgOCh (Ch = S or Se) compounds has been successfully achieved via the ion exchange of copper with silver in aqueous solutions, starting from the copper parent phase. Optical and electrical measurements of BiAgOCh powders confirm an increase in both the bandgap and the electrical resistivity, as compared to those of the copper compounds. The structure of the BiAgOS phase has been clearly examined. X-ray diffraction synchrotron measurements coupled with advanced high-resolution transmission electron microscopy analysis evidenced a Ag-deficient structure, as well as Bi-rich defects, both types of defects being oppositively charged. Silver atoms are also found in interstial sites, which explains the two-dimensional ionic conductivity. This structural study combined with theoretical calculations explains the intrinsic conductivity behavior of these semiconductors linked to the mutual compensation of both defect types in the structure and to the increase in the hole effective mass. This study shows the feasibility of modifying the optoelectronic properties of the BiMOCh compounds, with the goal of integrating them in heterojunction solar cells. Moreover, it provides very precise insight into the complexity of the relationship between structural defects and optoelectronic properties.

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Section: Bicuos Ag Biagos Cumentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Substituting Copper with Silver in the BiMOCh Layered Compounds (M = Cu or Ag; Ch = S, Se, or Te): Crystal, Electronic Structure, and Optoelectronic Properties

et al. 2018

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“…Apart from various attempts to enhance thermoelectric performance mentioned above, the interested readers are encouraged to refer to these extensive works that have been done on BiCuSeO systems, such as ultrathin BiCuSeO nanosheets [47], elastic and thermal properties [48,49], phonon transport [50,51], oxidation states [52], Cu vacancies [53,54], thermal stability [55,56], and the TEM study on BiCuSO and BiCuSeO that shows that Cu deficiency also plays a role in the stability and properties of those layered oxychalcogenides [54]. All of these studies largely enrich the understanding of BiCuSeO systems and have a great sense for future research.…”

Section: A Short Review For Various Attempts To Optimize Bicuseo Smentioning

confidence: 99%

BiCuSeO Thermoelectrics: An Update on Recent Progress and Perspective

et al. 2017

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A BiCuSeO system has been reported as a promising thermoelectric material and has attracted great attention in the thermoelectric community since 2010. Recently, several remarkable studies have been reported and the ZT of BiCuSeO was pushed to a higher level. It motivates us to systematically summarize the recent reports on the BiCuSeO system. In this short review, we start with several attempts to optimize thermoelectric properties of BiCuSeO. Then, we introduce several opinions to explore the origins of low thermal conductivity for BiCuSeO. Several approaches to enhance thermoelectric performance are also summarized, including modulation doping, introducing dual-vacancies, and dual-doping, etc. At last, we propose some possible strategies for enhancing thermoelectric performance of BiCuSeO in future research.

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“…[14][15][16][17] As a rational chemical approach, introduction of Cu vacancies could effectively enhance the electrical conductivity so as to improve thermoelectric performance of BiCuSeO. 18,19 In addition, the Cu defect also bring about some unique physical properties in BiCuSeO-based materials. For example, a large magnetoresistance, ferromagnetic and antiferromagnetic coupling, and charge transfer between the conduction and magnetic electrons caused by Cu vacancies were observed in BiCu 0.96 SeO.…”

Section: Introductionmentioning

confidence: 99%