物理学报Issue(21)：1-7,7.DOI:10.7498/aps.64.218101
Ca2+掺杂对CdO多晶热电性能的影响∗
High temp erature thermo electric p erformance of Ca2+dop ed CdO ceramics
摘要
Abstract
Oxide thermoelectric materials have been considered to be potential candidates in high-temperature thermoelectric power generation, however, their high thermal conductivity renders them inferior to the conventional thermoelectric materials and limit their practical application. In this paper, we successfully reduce the thermal conductivity of CdO polycrystals through Ca2+ doping, and the improvement in ZT is also obtained due to the low thermal conductivity. Cd1−xCaxO (x = 0, 0.01, 0.03, 0.08) polycrystals are synthesized by adding CaCO3 into CdO via conventional solid-state reaction method and their high-temperature thermoelectric properties are studied. XRD results reveal that all samples are composed of CdO polycrystals, and the lattice parameters increase with Ca2+ content due to the larger radius of Ca2+ as compared with that of Cd2+. Addition of CaCO3 can induce the formation of point defects as well as pores in the CdO polycrystals, thus inhibits the grain growth of CdO and induces the increase of grain boundaries. The main electron carriers in CdO are reported to be shallow level donor impurities formed by oxygen vacancies; as the Ca2+ concentration in Cd1−xCaxO increases, the conduction band minimum of the samples shifts upward and the level of donor impurity becomes deeper, finally resulting in the decrease of electron carrier concentration. Meanwhile, the reduced carrier concentration in the doped samples leads to the increase of both the electrical resistivity ρ and the absolute Seebeck coefficient |S|, while the electrical thermal conductivity κe will decrease with increasing Ca content. Investigations on the thermal properties of the obtained samples demonstrate that the introduction of Ca2+ is effective to suppress the thermal conductivity. The increment of pores and grain boundaries in the doped samples will enhance the long-wavelength phonon scattering, resulting in the decrease of phonon thermal conductivity κp. Furthermore, the point defects, which come from the mass and size differences between Ca and Cd atoms, also act as scattering centers and lead to a considerable decrease in phonon thermal conductivity. Due to the simultaneous reduction of both electrical and phonon thermal conductivity, the total thermal conductivity κ may substantially be suppressed, for example, the total thermal conductivity of Cd0.95Ca0.05O reaches 2.2 W·m−1·K−1 at 1000 K, a remarkable decrease as compared with pristine CdO, which is 3.6 W·m−1·K−1 measured at the same temperature. Benefiting from the drastically reduced thermal conductivity, Cd0.99Ca0.01O polycrystals can achieve a high ZT of 0.42 at 1000 K, 27% higher than the pure CdO, which is one of the best n-type oxide TE materials reported so far.关键词
热电/CdO多晶/热导率/ZTKey words
thermoelectric/CdO/thermal conductivity/ZT引用本文复制引用
刘冉,高琳洁,李龙江,翟胜军,王江龙,傅广生,王淑芳..Ca2+掺杂对CdO多晶热电性能的影响∗[J].物理学报,2015,(21):1-7,7.基金项目
国家自然科学基金(批准号:51372064)和河北省杰出青年科学基金(批准号:2013201249)资助的课题 （批准号:51372064）
