Hira Uzma, Han Li, Norrman Kion, Christensen Dennis Valbjørn, Pryds Nini, Sher Falak
Department of Chemistry and Chemical Engineering, SBA School of Science and Engineering, Lahore University of Management Sciences (LUMS) Lahore Pakistan
Department of Energy Conversion and Storage, Technical University of Denmark, Risø DTU Denmark
RSC Adv. 2018 Mar 28;8(22):12211-12221. doi: 10.1039/c8ra01691g. eCollection 2018 Mar 26.
The detailed crystal structures and high temperature thermoelectric properties of polycrystalline Ca Na Co W O (0 ≤ ≤ 0.075) samples have been investigated. Powder X-ray diffraction data show that all samples are phase pure, with no detectable traces of impurity. The diffraction peaks shift to lower angle values with increase in doping (), which is consistent with larger ionic radii of Na and W ions. X-ray photoelectron spectroscopy data reveal that a mixture of Co, Co and Co valence states are present in all samples. It has been observed that electrical resistivity (), Seebeck coefficient () and thermal conductivity () are all improved with dual doping of Na and W in CaCoO system. A maximum power factor (PF) of 2.71 × 10 W m K has been obtained for = 0.025 sample at 1000 K. The corresponding thermoelectric figure of merit () for = 0.025 sample is calculated to be 0.21 at 1000 K, which is ∼2.3 times higher than value of the undoped sample. These results suggest that Na and W dual doping is a promising approach for improving thermoelectric properties of CaCoO system.
研究了多晶CaₓNa₁₋ₓCo₄W₁₋ₓO₆（0 ≤ x ≤ 0.075）样品的详细晶体结构和高温热电性能。粉末X射线衍射数据表明，所有样品均为单相纯物质，未检测到杂质痕迹。随着掺杂量（x）的增加，衍射峰向低角度值移动，这与Na和W离子较大的离子半径一致。X射线光电子能谱数据表明，所有样品中均存在Co²⁺、Co³⁺和Co⁴⁺价态的混合物。据观察，在CaCoO体系中，通过Na和W的双重掺杂，电阻率（ρ）、塞贝克系数（S）和热导率（κ）均得到改善。对于x = 0.025的样品，在1000 K时获得了2.71×10⁻³ W m⁻¹ K⁻²的最大功率因子（PF）。x = 0.025样品在1000 K时的相应热电优值（ZT）经计算为0.21，约为未掺杂样品ZT值的2.3倍。这些结果表明，Na和W双重掺杂是改善CaCoO体系热电性能的一种有前景的方法。
