Grain Growth in Fe3O4

Sintering and microstructural evolution were studied in Fe₃O₄ as a model system for spinel ferrites. Fe₃O₄ powder, purified by the salt-crystallization method, was sintered to ～99.5% density in a CO-CO₂ atmosphere. The p _O2 Of the sintering atmosphere drastically affects the microstructure (grain size) of sintered Fe₃O₄ without significantly affecting density. The measured grain-boundary mobilities, M , of Fe₃O₄ fit the equation M=M ₀( T ) p _O2^?1/2 with M ₀( T ) = 2.5×10⁵ exp-(609kJ·mol-¹/ RT ](m/s)(N/m²)^?l. The grain-boundary migration process appeared to be pore-drag controlled, with lattice diffusion of oxygen as the most likely rate-limiting step.