Structural evolution of ball-milled ZnFe 2O 4

Abstract

Nanostructured zinc ferrite produced by milling in both low-energy and high-energy ball mills has been investigated by X-ray diffraction and Mössbauer effect spectroscopy. The lattice parameter of the milled products remains essentially unchanged from that of equilibrium ZnFe 2O 4 with the steady-state average particle size found to decrease to d=18(2) nm on low energy milling compared with d=8(1) nm on high energy milling. The room temperature Mössbauer spectra of the milled materials have been analysed using two doublets, one of which is considered to be associated primarily with the octahedral lattice sites. Spectral broadening is observed with decreasing particle size, particularly below d∼10 nm, for which the effects of magnetic hyperfine splitting become evident. The mean inversion parameter of nanostructured ZnFe 2O 4 is found to increase to c∼0.75 for particle sizes of d∼8 nm reflecting the systematic evolution of zinc ferrite from its normal spinel structure towards an inverse spinel structure on mechanical treatment as observed previously. The other factors which contribute to the Mössbauer spectra of nanostructured ZnFe 2O 4 ( d∼8–70 nm) are discussed.