Grain Growth in Fe ₃ O ₄

Abstract

Sintering and microstructural evolution were studied in Fe 3 O 4 as a model system for spinel ferrites. Fe 3 O 4 powder, purified by the salt‐crystallization method, was sintered to ∼99.5% density in a CO‐CO 2 atmosphere. The p O2 Of the sintering atmosphere drastically affects the microstructure (grain size) of sintered Fe 3 O 4 without significantly affecting density. The measured grain‐boundary mobilities, M , of Fe 3 O 4 fit the equation M=M 0 ( T ) p O2 −1/2 with M 0 ( T ) = 2.5×10 5 exp[‐(609kJ·mol‐ 1 / RT ](m/s)(N/m 2 ) −l . The grain‐boundary migration process appeared to be pore‐drag controlled, with lattice diffusion of oxygen as the most likely rate‐limiting step.