Growth of hafnium and zirconium silicides by reactive diffusion

Diffusion controlled growth of the phases in Hf–Si and Zr–Si systems are studied by bulk diffusion couple technique. Only two phases grow in the interdiffusion zone, although several phases are present in both the systems. The location of the Kirkendall marker plane, detected based on the grain morphology, indicates that disilicides grow by the diffusion of Si. Diffusion of the metal species in these phases is negligible. This indicates that vacancies are present mainly on the Si sublattice. The activation energies for integrated diffusion coefficients in the HfSi₂ and ZrSi₂ are estimated as 394 ± 37 and 346 ± 34 kJ mol⁻¹, respectively. The same is calculated for the HfSi phase as 485 ± 42 kJ mol⁻¹. The activation energies for Si tracer diffusion in the HfSi₂ and ZrSi₂ phases are estimated as 430 ± 36 and 348 ± 34 kJ mol⁻¹, respectively. - Highlights: • Growth mechanisms of hafnium and Zr silicides by reactive diffusion are explained. • Only two phases are grown in the interdiffusion zone. • Diffusion parameters are estimated. • Location of the Kirkendall marker plane indicates that Si is the faster diffusing species in disilicides. • This indicates that vacancies are present on the Si sublattice in disilicides