Phase-transition kinetics of formation of β-Fe₅Ge₃ in isothermal sintering

The phase-transition kinetics during isothermal sintering of the β-Fe₅Ge₃ phase from a mixture of the pure elements, Fe and Ge was investigated. The phases: α-FeGe, ε-Fe₃Ge and η- Fe_xGe were found to appear in the course of phase-transformations towards β-Fe₅Ge₃. These intermediate phases were identified by means of X-ray diffraction and Mössbauer spectroscopy. Using a differential dilatometer, the densification kinetics were established at 535, 600, 700 and 800°C and verified by density measurements. Diffusion in this sintering process is unidirectional in the sense that Ge atoms diffuse into the Fe lattice but very little vice versa. The apparent activation energy of the densification process is 58 kcal/mol.