Thermal treatment of the particles during the preparation could cause sintering and grain growth.
As grain boundary diffusion cloud be the rate determining step, during reaction the grain structure would be expected to influence kinetics
, explaining the results shown in Fig. 4. It must be highlighted that FeP was not subjected to sintering at 1250 C as were Fe40-80 and Fe80-160. Operation at high temperature favoured the sintering of the sub-micron iron oxide powders.