Abstract: The precursors ground by planetary ball milling at room temperature were calcined to obtain NiFe₂O₄ nanopowder. The effect of calcination temperature on the particle phase and morphology and the mechanisms of solid-state reaction were studied in detail. The results show that the activation energy of grain growth during calcination process is 12.08kJ·mol^-1， indicating that the predominant mass transport mechanism is interfacial diffusion. The particles calcined at 700℃ showed strong agglomeration and low crystallinity with flaky amorphous compounds. The NiFe₂O₄ nanopowder calcined at 750℃ for 1h is of single phase with a particle size range of 35-85nm. The grains grew obviously when the calcination temperature increased to over 800℃. The main compositions of the precursor are Fe₂O₃， NiO and NiFe₂O₄. The low crystallinity of reaction products indicates the solid state reaction is not complete. The existence of salt particles can suppress grain growth， and thus decrease the particle size.

Key words: NiFe₂O₄, nanopowder, low temperature solid-state reaction, ball milling grinding, calcination temperature, mechanism