Xigui Sun

Cd-doping a facile approach for better thermoelectric transport properties of BiCuSeO oxyselenides

BiCuSeO-based thermoelectric materials have spurred tremendous interest among the thermoelectric community due to their ultra-low thermal conductivity and relatively large Seebeck coefficient (S). In this work, we have reported the effect of Cd-doping at the Bi site, instead of the previously studied Cu site, on the thermoelectric performance of BiCuSeO by modifying the insulating layer. While maintaining good phase purity, Cd was successfully doped at the Bi site as confirmed by X-ray absorption fine structure spectroscopy. The Cd-doping substantially improves the electrical conductivity by a factor of 20 through bond anharmonicity at room temperature while increasing the Cd concentration over 5%. Further, the incorporation of the lighter atom at the Bi site creates phonon scattering centers and results in weak bonding between the layers, resulting in a remarkable perturbation of the local geometric and electronic structure. BiCuSeO with 5% Cd-doping maintains a large S and a high electrical conductivity up to 923 K and exhibits the highest power factor values (600 μW m−1 K−2 at 323 K and 447 μW m−1 K−2 at 923 K) and the largest ZT (0.98 at 923 K). Cd-doping at the Bi site in p-type thermoelectric BiCuSeO was shown to be a very good technique for improving the thermoelectric performance and could be extended to other thermoelectric materials to enhance the efficiency of thermoelectric devices for energy-harvesting.

Interface and Strain Energy Revolution Texture Map To Predict Structure and Optical Properties of Sputtered PbSe Thin Films

The preferred growth orientation of the sputtered lead selenide (PbSe) thin films on Si(100) substrates was thermodynamically simulated and calculated on the basis of the density functional theory. The results showed that the total free energy variation during the grain growth is dominated by the interface and strain energy minimization under certain conditions, indicating that the preferred growth orientation and related optical properties of the PbSe thin films can be effectively modified by these two energy variations. Thermodynamically, the PbSe[200] and PbSe[220] preferred orientations are obtained when the interface and strain energy minimization dominate the total free energy variation, respectively. A texture map related to the interface and strain energy revolution was obtained, which can be used to predict the structure and optical properties of the sputtered PbSe thin films, and its applicability was confirmed by the real X-ray diffraction and Fourier transform infrared spectroscopy experimental results of four midfrequency sputtered PbSe thin films with designed thickness and microstrain deposited on Si(100) substrates.

Pronounced effect of ZnTe nanoinclusions on thermoelectric properties of Cu 2−x Se chalcogenides

Metal chalcogenides especially Cu2−xSe has gained much attention in thermoelectric community due to its complex crystal structure and superionic behavior. Here, we report a facile method to improve the thermoelectric efficiency by introducing ZnTe nanoinclusions into the matrix of Cu2−xSe. As a result, a substantial improvement of 32% in electrical conductivity of Cu2−xSe-ZnTe composite is observed. The increase in electrical conductivity is at the expense of Seebeck coefficient, which slightly decreases the power factor of the composite samples than that of pure Cu2−xSe. Furthermore, the introduction of secondary phase facilitates in declining the total thermal conductivity of Cu2−xSe-ZnTe composite up to 34% by suppressing the lattice thermal contributions. Thus, the moderate power factor and lower thermal conductivity values result in an improved figure of merit (zT) value of ∼0.40 in mid-range temperature (750 K) for Cu2−xSe-ZnTe composite with 10 wt.% of ZnTe, which is about 40% higher than that of its pure counterpart. Hence, it is believed that the incorporation of ZnTe nanoinclusions in the matrix of Cu2−xSe may be an important route to improve the thermoelectric properties of Cu2−xSe based compounds.摘要由于具有复杂的晶体结构和超离子导体行为, 金属硫属化合物特别是Cu2−xSe在热电领域得到了广泛的关注. 本文报道了一种简单易行的提高热电效率的方法:在基体材料Cu2−xSe中添加纳米ZnTe插层, 用来提高Cu2−xSe材料的热电性能. 实验结果表明, Cu2−xSe-ZnTe复合材料的电导率提高了32%, 电导率的增加牺牲了塞贝克系数, 导致复合材料的功率因子稍微低于纯Cu2−xSe基体材料; 第二相的引入抑制了晶格热扩散, 使得Cu2−xSe-ZnTe复合材料的热导率降低了34%. 由此可知, 适中的功率因子和较低的热导率致使含有10 wt.%ZnTe的Cu2−xSe-ZnTe复合材料在中温条件(750 K)下的zT值提高至0.40, 相比于纯Cu2−xSe基体材料该数值提高了40%. 因此, 向Cu2−xSe材料中添加纳米ZnTe插层, 是提高Cu2−xSe基材料热电性能的一个有效途径.

Enhanced thermoelectric transport properties of La0.98Sr0.02CoO3-BiCuSeO composite

We report a facile method to enhance the thermoelectric efficiency of La0.98Sr0.02CoO3 by introducing BiCuSeO as a secondary phase with ultra-low thermal conductivity. Inclusion of secondary phase results in reducing the total thermal conductivity by suppressing the lattice and electronic thermal conductivities and also contributes to enhancement in the Seebeck coefficient. The wide grain size distribution of La0.98Sr0.02CoO3-BiCuSeO composite facilitates in breaking the interlinked transport properties through increased scattering of different wavelength phonons. The combined effect of enhanced Seebeck coefficient and ultra-low thermal conductivity, results in an improved ZT value of 0.07 at 923 K. The proposed strategy can be opted for improvement in the thermoelectric efficiency of other thermoelectric materials as well.

Pronounced effect of ZnTe nanoinclusions on thermoelectric properties of Cu2−xx

Metal chalcogenides especially Cu2−xSe has gained much attention in thermoelectric community due to its complex crystal structure and superionic behavior. Here, we report a facile method to improve the thermoelectric efficiency by introducing ZnTe nanoinclusions into the matrix of Cu2−xSe. As a result, a substantial improvement of 32% in electrical conductivity of Cu2−xSe-ZnTe composite is observed. The increase in electrical conductivity is at the expense of Seebeck coefficient, which slightly decreases the power factor of the composite samples than that of pure Cu2−xSe. Furthermore, the introduction of secondary phase facilitates in declining the total thermal conductivity of Cu2−xSe-ZnTe composite up to 34% by suppressing the lattice thermal contributions. Thus, the moderate power factor and lower thermal conductivity values result in an improved figure of merit (zT) value of ∼0.40 in mid-range temperature (750 K) for Cu2−xSe-ZnTe composite with 10 wt.% of ZnTe, which is about 40% higher than that of its pure counterpart. Hence, it is believed that the incorporation of ZnTe nanoinclusions in the matrix of Cu2−xSe may be an important route to improve the thermoelectric properties of Cu2−xSe based compounds.摘要由于具有复杂的晶体结构和超离子导体行为, 金属硫属化合物特别是Cu2−xSe在热电领域得到了广泛的关注. 本文报道了一种简单易行的提高热电效率的方法:在基体材料Cu2−xSe中添加纳米ZnTe插层, 用来提高Cu2−xSe材料的热电性能. 实验结果表明, Cu2−xSe-ZnTe复合材料的电导率提高了32%, 电导率的增加牺牲了塞贝克系数, 导致复合材料的功率因子稍微低于纯Cu2−xSe基体材料; 第二相的引入抑制了晶格热扩散, 使得Cu2−xSe-ZnTe复合材料的热导率降低了34%. 由此可知, 适中的功率因子和较低的热导率致使含有10 wt.%ZnTe的Cu2−xSe-ZnTe复合材料在中温条件(750 K)下的zT值提高至0.40, 相比于纯Cu2−xSe基体材料该数值提高了40%. 因此, 向Cu2−xSe材料中添加纳米ZnTe插层, 是提高Cu2−xSe基材料热电性能的一个有效途径.