Ga填充n型方钴矿化合物的结构及热电性能

用熔融退火结合放电等离子烧结(SPS)技术制备了具有不同Ga填充含量的Ga_xCo₄Sb₁₂方钴矿化合物，研究了不同Ga含量对其热电传输特性的影响规律. Rietveld结构解析表明,Ga占据晶体学2a空洞位置，Ga填充上限约为0.22，当Ga的名义组成x≤0.25时，样品的电导率、室温载流子浓度N_p随Ga含量的增加而增加，Seebeck系数随Ga含量的增加而减小. 室温下霍尔测试表明，每一个Ga授予框架0.9个电子，比Ga的氧化价态Ga³⁺小得多. 由于Ga离子半径相对较小，致使Ga填充方钴矿化合物的热导率κ及晶格热导率κ_L较其他元素填充的方钴矿化合物低. 当x＝0.22时对应的样品在300K时的热导率和晶格热导率分别为3.05Wm^-1·K^-1和 2.86Wm^-1·K^-1.在600K下Ga_0.22Co_4.0Sb_12.0样品晶格热导率达到最小，为1.83Wm^-1·K^-1，最大热电优值Z，在560K处达1.31×10^-3K^-1.关键词：skutterudite化合物Ga原子填充结构热电性能

Structure and thermoelectric properties of n-type GaxCo4Sb12 skutterudite compounds

Ga-filled Ga_xCo₄Sb₁₂ skutterudite compounds with different Ga contents were synthesized by combining a melting quenching-diffusion-annealing procedure with spark plasma sintering (SPS). The effects of Ga content on thermoelectric properties were investigated. The results of Rietveld refinement indicated that the Ga is located in the 2a void site. The solubility limit of the Ga filling voids in CoSb₃ was found to be close to 0.22. The electrical conductivity and the room temperature carrier concentration N_p of the samples increase with the increasing Ga content for Ga filled Ga_xCo₄Sb₁₂ skutterudite compounds with x≤0.25, while the Seebeck coefficient decreases with the increasing Ga content. Room temperature Hall measurements show that each Ga atom donates approximately 0.9 electrons, which is significantly less than that of the Ga oxidation state (3+). Ga-filled skutterudites exhibit much lower thermal conductivity and lattice thermal conductivity in comparison with that of other partially filled skutterudites due to the smaller radius of Ga³⁺ ions compared with that of other filling atoms. The thermal conductivity and lattice thermal conductivity of Ga_0.22Co₄Sb₁₂ compound are 3.05Wm^-1·K^-1 and 2.86Wm^-1·K^-1 respectively. The Ga_0.22Co₄Sb₁₂ compound possesses the lowest lattice thermal conductivity at 600K. It is as low as 1.83Wm^-1·K^-1. The maximum Z value of 1.31×10^-3K^-1 is obtained at 560K for Ga_0.22Co₄Sb₁₂.