Yiderigu Jin, Yibole Hargen, Bao Lingbo, Bao Lingling, Guillou François
College of Physics and Electronic Information, Inner Mongolia Key Laboratory for Physics and Chemistry of Functional Materials, Inner Mongolia Normal University, 81 Zhaowuda Rd., Hohhot 010022, China.
Materials (Basel). 2024 May 21;17(11):2476. doi: 10.3390/ma17112476.
(Fe,Co)(P,Si) quaternary compounds combine large uniaxial magnetocrystalline anisotropy, significant saturation magnetization and tunable Curie temperature, making them attractive for permanent magnet applications. Single crystals or conventionally prepared bulk polycrystalline (Fe,Co)(P,Si) samples do not, however, show a significant coercivity. Here, after a ball-milling stage of elemental precursors, we optimize the sintering temperature and duration during the solid-state synthesis of bulk FeCoPSi compounds so as to obtain coercivity in bulk samples. We pay special attention to shortening the heat treatment in order to limit grain growth. Powder X-ray diffraction experiments demonstrate that a sintering of a few minutes is sufficient to form the desired FeP-type hexagonal structure with limited secondary-phase content (~5 wt.%). Coercivity is achieved in bulk FeCoPSi quaternary compounds by shortening the heat treatment. Surprisingly, the largest coercivities are observed in the samples presenting large amounts of secondary-phase content (>5 wt.%). In addition to the shape of the virgin magnetization curve, this may indicate a dominant wall-pining coercivity mechanism. Despite a tenfold improvement of the coercive fields for bulk samples, the achieved performances remain modest ( ≈ 0.6 kOe at room temperature). These results nonetheless establish a benchmark for future developments of (Fe,Co)(P,Si) compounds as permanent magnets.
(Fe,Co)(P,Si) 四元化合物兼具大的单轴磁晶各向异性、显著的饱和磁化强度和可调节的居里温度，使其在永磁应用方面颇具吸引力。然而，单晶或传统制备的块状多晶 (Fe,Co)(P,Si) 样品并未表现出显著的矫顽力。在此，在对元素前驱体进行球磨阶段之后，我们在块状 FeCoPSi 化合物的固态合成过程中优化烧结温度和持续时间，以便在块状样品中获得矫顽力。我们特别注意缩短热处理时间以限制晶粒生长。粉末 X 射线衍射实验表明，几分钟的烧结足以形成所需的具有有限第二相含量（约 5 wt.%）的 FeP 型六方结构。通过缩短热处理时间，在块状 FeCoPSi 四元化合物中实现了矫顽力。令人惊讶的是，在具有大量第二相含量（>5 wt.%）的样品中观察到了最大的矫顽力。除了初始磁化曲线的形状外，这可能表明主导的壁钉扎矫顽力机制。尽管块状样品的矫顽场提高了十倍，但所实现的性能仍然一般（室温下约为 0.6 kOe）。尽管如此，这些结果为 (Fe,Co)(P,Si) 化合物作为永磁体的未来发展确立了一个基准。
