Zuñiga-Puelles E, Cardoso-Gil R, Bobnar M, Veremchuk I, Himcinschi C, Hennig C, Kortus J, Heide G, Gumeniuk R
Institut für Experimentelle Physik, TU Bergakademie Freiberg, Leipziger Str. 23, 09599 Freiberg, Germany.
Max-Planck-Institut für Chemische Physik fester Stoffe, Nöthnitzer Str. 40, 01187 Dresden, Germany.
Dalton Trans. 2019 Jul 16;48(28):10703-10713. doi: 10.1039/c9dt01902b.
Synthetic bulk and natural pyrite from the hydrothermal mine in Schönbrunn (Saxony, Germany) are confirmed to be stoichiometric FeS2 compounds and stable (for thermoelectric applications) up to ∼600 K by combined thermal, chemical, spectroscopic and X-ray diffraction analyses. Natural pyrite with a small amount (<0.6 wt%) of well-defined transition metal carbonates revealed characteristics of a nondegenerate semiconductor and is suitable as a model system for the investigation of thermoelectric performance. In the temperature range 50-600 K both natural and synthetic high quality bulk FeS2 samples show electrical resistivity and Seebeck coefficients varying within 220-5 × 10-3 Ω m and 4 - (-450) μV K-1, respectively. The large thermal conductivity (∼40 W m-1 K-1 at 300 K) is exclusively due to phononic contribution, showing a well pronounced maximum centered at ∼75 K for natural pyrite (grain size ≤5 mm). It becomes almost completely suppressed in the sintered bulk samples due to the increase of point defect concentration and additional scattering on the grain boundaries (grain size ≤100 μm). The thermoelectric performance of pure pyrite with ZT ∼ 10-6 at 600 K is indeed by a factor of ∼1000 worse than those reported earlier for some minerals and synthetic samples.
通过热分析、化学分析、光谱分析和X射线衍射分析相结合，证实来自德国萨克森州舍恩布伦热液矿的合成块状黄铁矿和天然黄铁矿为化学计量比的FeS₂化合物，并且（对于热电应用而言）在高达约600 K的温度下是稳定的。含有少量（<0.6 wt%）明确过渡金属碳酸盐的天然黄铁矿表现出非简并半导体的特性，适合作为研究热电性能的模型系统。在50 - 600 K的温度范围内，天然和合成的高质量块状FeS₂样品的电阻率和塞贝克系数分别在220 - 5×10⁻³ Ω·m和4 - (-450) μV K⁻¹范围内变化。较大的热导率（300 K时约为40 W m⁻¹ K⁻¹）完全归因于声子贡献，天然黄铁矿（晶粒尺寸≤5 mm）在约75 K处有一个明显的最大值。由于点缺陷浓度的增加以及晶界（晶粒尺寸≤100 μm）上的额外散射，在烧结块状样品中热导率几乎被完全抑制。纯黄铁矿在600 K时的热电性能ZT约为10⁻⁶，确实比之前报道的一些矿物和合成样品差约1000倍。
