Co-based Heusler alloys are attracting considerable interest as they were found to be suitable for spin-injection processes, and for the generation of spin-polarized currents via spin-Seebeck effect. Co₂HfSn has been proved to be one of the most promising candidates for this application, since it combines remarkable half-metallic properties, compositional and doping versatility, ease of preparation, high Curie temperature, and sufficiently high Seebeck coefficient. In this work, the Co₂HfSn Heusler compound was synthesized by rapid solidification (melt-spinning) followed by spark plasma sintering. Electron backscattered diffraction (EBSD) analysis was performed, providing useful information on the microstructure and grain size distribution which result from such processing route. An average grain size of approximately 5 μm was observed. The electronic and thermal transport properties were then measured, and the thermoelectric figure of merit zT was experimentally estimated for the first time, having a maximum value of 0.040 at 800 K. The electrical conductivity and the charge carrier concentration were measured down to 2 K to collect evidence on the shape of the electronic density of states in proximity of the Fermi level at temperatures close to absolute zero. A change of regime of the electrical conductivity at low temperatures was found and explained in terms of a modification of the electron scattering mechanisms, due to a crossover from a half-metallic to a conductive state at 75 K. Finally, the transport, elastic and vibrational properties were calculated using Density Functional Theory (DFT). Properties such as the Seebeck coefficient and the electronic thermal conductivity were evaluated using DFT-calculated electronic bands within the framework of Boltzmann transport theory. Vibrational properties, such as phonon band structure, density of states and heat capacity were computed in the harmonic approximation, using DFT to calculate the force constants matrix. Results from calculations of the elastic moduli enabled us to apply Slack's model for the estimation the lattice thermal conductivity. By combining experimental measurements with DFT calculations, we obtained consistent results that offer a deeper understanding of the properties of this compound at both low and high temperatures.

钴基霍斯勒合金引起了人们极大的兴趣，因为它们被发现适用于自旋注入过程，以及通过自旋塞贝克效应产生自旋极化电流。Co ₂ HfSn 已被证明是该应用中最有前途的候选材料之一，因为它结合了卓越的半金属特性、成分和掺杂的多功能性、易于制备、高居里温度和足够高的塞贝克系数。在这项工作中，Co ₂ HfSn Heusler 化合物通过快速凝固（熔融纺丝）和随后的放电等离子烧结来合成。进行了电子背散射衍射（EBSD）分析，提供了有关由这种加工路线产生的微观结构和晶粒尺寸分布的有用信息。观察到平均晶粒尺寸约为5μm。然后测量了电子和热传输特性，并首次通过实验估算了热电品质因数 zT，在 800 K 时具有最大值 0.040。在低至 2 K 的温度下测量了电导率和载流子浓度，收集有关在接近绝对零的温度下费米能级附近的电子态密度形状的证据。由于在 75 K 时从半金属状态转变为导电状态，发现了低温下电导率状态的变化，并根据电子散射机制的修改进行了解释。最后，输运、弹性和使用密度泛函理论（DFT）计算振动特性。在玻尔兹曼输运理论框架内，使用 DFT 计算的电子能带评估了塞贝克系数和电子热导率等特性。振动特性，如声子能带结构、态密度和热容，在谐波近似中计算，使用 DFT 计算力常数矩阵。弹性模量的计算结果使我们能够应用 Slack 模型来估计晶格热导率。通过将实验测量与 DFT 计算相结合，我们获得了一致的结果，可以更深入地了解该化合物在低温和高温下的特性。