WPI International Center for Materials Nanoarchitechtonics (WPI-MANA) , National Institute for Materials Science (NIMS) , Namiki 1-1 , Tsukuba 305-0044 , Ibaraki , Japan.
National Institute for Materials Science (NIMS) , Sengen 1-2-1 , Tsukuba 305-0047 , Ibaraki , Japan.
Inorg Chem. 2018 May 7;57(9):5258-5266. doi: 10.1021/acs.inorgchem.8b00301. Epub 2018 Apr 9.
Thermoelectric properties of CuMnTe, which is antiferromagnetic with a Néel temperature T = 50 K and crystallizes in a spinel-related structure, have been investigated comprehensively here. The phase transition occurring at temperatures 463 and 723 K is studied by high-temperature X-ray diffraction (XRD) and differential scanning calorimetry (DSC), and its effect on thermoelectric properties is examined. Hypothetically CuMnTe is semiconducting according to the formula (Cu)(Mn)(Te), while experimentally it shows p-type metallic conduction behavior, exhibiting electrical conductivity σ = 2500 Ω cm and Seebeck coefficient α = 20 μV K at 325 K. Herein, we show that the carrier concentration and thus the thermoelectric transport properties could be further optimized through adding electron donors such as excess Mn. Discussions are made on the physical parameters contributing to the low thermal conductivity, including Debye temperature, speed of sound, and the Grüneisen parameter. As a result of simultaneously boosted power factor and reduced thermal conductivity, a moderately high zT = 0.65 at 680 K is obtained in an excess Mn\In co-added sample, amounting to 5 times that of the pristine CuMnTe. This value ( zT = 0.65) is the best result ever reported for spinel and spinel-related chalcogenides.
我们在此全面研究了具有反铁磁特性（奈尔温度为 T = 50 K）并结晶于尖晶石相关结构的 CuMnTe 的热电性质。通过高温 X 射线衍射（XRD）和差示扫描量热法（DSC）研究了在 463 和 723 K 温度下发生的相变，并考察了其对热电性质的影响。根据公式 (Cu)(Mn)(Te)，理论上 CuMnTe 应为半导体，但实际上它表现出 p 型金属导电行为，在 325 K 时电导率 σ = 2500 Ω cm，塞贝克系数 α = 20 μV K。在此，我们表明通过添加电子施主（如过量的 Mn）可以进一步优化载流子浓度，从而优化热电输运性质。对有助于降低热导率的物理参数（德拜温度、声速和格林艾森参数）进行了讨论。由于同时提高了功率因子和降低了热导率，在过量 Mn 和 In 共添加的样品中获得了在 680 K 时适度高的 zT = 0.65，是原始 CuMnTe 的 5 倍。这一值（zT = 0.65）是迄今为止报道的尖晶石和尖晶石相关硫族化物的最佳结果。
