Paschinger W, Rogl G, Grytsiv A, Michor H, Heinrich P R, Müller H, Puchegger S, Klobes B, Hermann R P, Reinecker M, Eisenmenger-Sitter Ch, Broz P, Bauer E, Giester G, Zehetbauer M, Rogl P F
Institute of Materials Chemistry & Research, University of Vienna, Währinger Straße 42, A-1090 Vienna, Austria.
Institute for Solid State Physics, TU-Wien, Wiedner Hauptstr. 8, A-1040 Vienna, Austria.
Dalton Trans. 2016 Jul 5;45(27):11071-100. doi: 10.1039/c6dt01298a.
Novel filled skutterudites BayNi4Sb12-xSnx (ymax = 0.93) have been prepared by arc melting followed by annealing at 250, 350 and 450 °C up to 30 days in vacuum-sealed quartz vials. Extension of the homogeneity region, solidus temperatures and structural investigations were performed for the skutterudite phase in the ternary Ni-Sn-Sb and in the quaternary Ba-Ni-Sb-Sn systems. Phase equilibria in the Ni-Sn-Sb system at 450 °C were established by means of Electron Probe Microanalysis (EPMA) and X-ray Powder Diffraction (XPD). With rather small cages Ni4(Sb,Sn)12, the Ba-Ni-Sn-Sb skutterudite system is perfectly suited to study the influence of filler atoms on the phonon thermal conductivity. Single-phase samples with the composition Ni4Sb8.2Sn3.8, Ba0.42Ni4Sb8.2Sn3.8 and Ba0.92Ni4Sb6.7Sn5.3 were used to measure their physical properties, i.e. temperature dependent electrical resistivity, Seebeck coefficient and thermal conductivity. The resistivity data demonstrate a crossover from metallic to semiconducting behaviour. The corresponding gap width was extracted from the maxima in the Seebeck coefficient data as a function of temperature. Single crystal X-ray structure analyses at 100, 200 and 300 K revealed the thermal expansion coefficients as well as Einstein and Debye temperatures for Ba0.73Ni4Sb8.1Sn3.9 and Ba0.95Ni4Sb6.1Sn5.9. These data were in accordance with the Debye temperatures obtained from the specific heat (4.4 K < T < 140 K) and Mössbauer spectroscopy (10 K < T < 290 K). Rather small atom displacement parameters for the Ba filler atoms indicate a severe reduction in the "rattling behaviour" consistent with the high levels of lattice thermal conductivity. The elastic moduli, collected from Resonant Ultrasonic Spectroscopy ranged from 100 GPa for Ni4Sb8.2Sn3.8 to 116 GPa for Ba0.92Ni4Sb6.7Sn5.3. The thermal expansion coefficients were 11.8 × 10(-6) K(-1) for Ni4Sb8.2Sn3.8 and 13.8 × 10(-6) K(-1) for Ba0.92Ni4Sb6.7Sn5.3. The room temperature Vickers hardness values vary within the range from 2.6 GPa to 4.7 GPa. Severe plastic deformation via high-pressure torsion was used to introduce nanostructuring; however, the physical properties before and after HPT showed no significant effect on the materials thermoelectric behaviour.
通过电弧熔炼，然后在真空密封石英管中于250、350和450℃退火长达30天，制备了新型填充方钴矿BaNi4Sb12 - xSnx（ymax = 0.93）。对三元Ni - Sn - Sb和四元Ba - Ni - Sb - Sn体系中的方钴矿相进行了均匀性区域扩展、固相线温度和结构研究。借助电子探针微分析（EPMA）和X射线粉末衍射（XPD）确定了Ni - Sn - Sb体系在450℃时的相平衡。由于具有相当小的笼状结构Ni4(Sb,Sn)12，Ba - Ni - Sn - Sb方钴矿体系非常适合研究填充原子对声子热导率的影响。使用组成分别为Ni4Sb8.2Sn3.8、Ba0.42Ni4Sb8.2Sn3.8和Ba0.92Ni4Sb6.7Sn5.3的单相样品来测量它们的物理性质，即与温度相关的电阻率、塞贝克系数和热导率。电阻率数据表明从金属行为转变为半导体行为。从塞贝克系数数据的最大值作为温度的函数中提取了相应的能隙宽度。在100、200和300K下进行的单晶X射线结构分析揭示了Ba0.73Ni4Sb8.1Sn3.9和Ba0.95Ni4Sb6.1Sn5.9的热膨胀系数以及爱因斯坦温度和德拜温度。这些数据与从比热（4.4K < T < 140K）和穆斯堡尔谱（10K < T < 290K）获得的德拜温度一致。Ba填充原子相当小的原子位移参数表明“晃动行为”严重减少，这与高晶格热导率水平一致。从共振超声光谱收集的弹性模量范围从Ni4Sb8.2Sn3.8的100GPa到Ba0.92Ni4Sb6.7Sn5.3的116GPa。热膨胀系数对于Ni4Sb8.2Sn3.8为11.8×10(-六)K(-1)，对于Ba0.92Ni4Sb6.7Sn5.3为13.8×10(-六)K(-1)。室温维氏硬度值在2.6GPa至4.7GPa范围内变化。通过高压扭转进行严重塑性变形以引入纳米结构；然而，高压扭转前后的物理性质对材料的热电行为没有显著影响。
