Optimizing the Power Factor of FeSi2 Alloy by Achieving Flower-Like Surface Morphology Using Post-Growth Annealing

In this work, we have successfully optimized the power factor value for an FeSi₂ alloy by achieving a flower-like surface morphology. The samples used in this study were prepared using a solid-state reaction method. Fe and Si powders were mixed in a weight ratio of 2:1, and pellets were formed using a high-pressure press. The pellets were annealed at different temperatures in the range of 500–1000°C for 1 h using an air muffle furnace. X-ray diffraction (XRD) data confirmed the tetragonal lattice structure of all samples, and it was further evident that the crystal structure degraded as the annealing temperature increased to 900°C and 1000°C. A very high Seebeck coefficient (470 µV/K) was achieved for the sample annealed at 1000°C due to the emergence of a flower-like surface morphology with high-temperature annealing, as verified by scanning electron microscopy (SEM) images. On the other hand, electrical conductivity data suggested a decreasing trend with annealing temperature, because oxide-based insulating phases developed at a high annealing temperature due to the involvement of oxygen during the annealing process. However, the decreasing trend in electrical conductivity is not as great as the increasing behaviour of the Seebeck coefficient. Therefore, an optimized power factor value (3.5 × 10⁻⁵ W/m·K²) was achieved at the optimal annealing temperature of 700°C.