| 학회 | 한국재료학회 |
| 학술대회 | 2018년 가을 (11/07 ~ 11/09, 여수 디오션리조트) |
| 권호 | 24권 2호 |
| 발표분야 | H. 한-일 재료공학(KJMST 2018) |
| 제목 | Electrical structure and thermal properties of ZrCuSiAs type mixed anion layered compounds |
| 초록 | A thermoelectric material is evaluated by the dimensionless figure of merit ZT=S2σT/κ; The (S,σ,κ,T) are Seebeck coefficient, electrical conductivity, thermal conductivity, and absolute temperature, respectively. “ZT ≧ 1” is a so-called criterion for practical application of thermoelectric materials. Compounds, which exhibit larger S, larger σ and smaller κ, have been required. The electronic phases of mixed anion layered compounds (MALCs) with ZrCuSiAs-type structure have interested a great number of researchers due to MALCs’ functional properties; i.e. transparent p-type conductivity, iron based superconductivity, and thermoelectricity. For thermoelectric material, in 2010, Zhao et al reported BiCuSeO with ZrCuSiAs-type structure as a promising thermoelectric material. In 2013, J. Sui et al reported ZT of Bi1-xBaxCuSeO had reached at 1.4. However, a mechanism of carrier doping is still controversial due to off-stoichiometry of the MALCs. In 2010, Hiramatsu et al reported that the main origin of heavy hole doping of LaCuSeO with ZrCuSiAs-type structure is the off-stoichiometry of Cu and Se. In 2014, Goto reported that the Cu deficiency have a crucial impact on the electrical transport properties of a LaCuSO. In 2018, Kato et al also reported that off stoichiometric polycrystalline LaCuSeO, which is a representative MALC, exhibit p-type carrier doped semiconducting phase. In this research, electronic structures of SrMnPnF and BaMnPnF (Pn=P, As, Sb, Bi), which are categorized as MALCs and show the identical space group with BiCuSeO (space group: P4/nmm), are demonstrated based on density functional theory (DFT). The DFT calculations were performed using the Vienna Ab initio Simulation Package (VASP) adopting the projector-augmented wave (PAW) method. The exchange correlation potential was approximated within the generalized gradient approximation (GGA) by the Perdew-Becke-Ernzerhof (PBE) method. The spin–orbit coupling (SOC) were considered due to the heavy elements included in the materials. Transport properties of the MALCs were calculated based on Boltzmann transport equation. S and σ are evaluated by using the semi-classical Boltzmann transport theory with the constant relaxation time approximation, which is implemented in the BoltzTraP2. As a result, DFT calculations suggested the spin structure of SrMnPnF and BaMnPnF (Pn=P, As, Sb, Bi); magnetic checkerboard pattern of the antiferromagnetic Mn is most favourable state. Electronic structure of MALCs showed that degenerated d orbits demonstrates enhance Seebeck coefficient. Our results suggest SrMnSbF, BaMnAsF and BaMnSbF as mother compounds for high ZT thermoelectric materials. Theoretical κ is required to predict ZT more precisely. |
| 저자 | Manami NAKANISHI1, Masanori MATOBA2, Yoichi KAMIHARA3 |
| 소속 | 1Department of Applied Physics and Physico-Informatics, 2Faculty of Science and Technology, 3Keio Univ. |
| 키워드 | thermoelectricity; density functional theory; boltzmann equation; mixed anion layered compounds |
