Observations of ultrafine ZnFe2O4 particles with transmission electron microscopy

Abstract

Ultrafine ZnFe2O4 particles less than 10 nm in diameter formed by the coprecipitation method were observed using transmission electron microscopy. The chemical composition of these particles was consistent with that of the stoichiometric bulk material. The apparent lattice structure could be observed. These observations revealed that particles 5 nm in diameter were fine, defect-free, and cubic single crystals having a spinel structure. The particle surface became more and more circular with decreasing particle size. Even a particle as small as 2 nm was seen to be homogeneous and possess a spinel structure. To determine the particle size it was necessary to disperse particles by covering their surfaces with a double-adsorbed surfactant film. The particle size distribution was seen to be approximately log normal.