Radiation-induced lattice relaxation in alpha -Fe_2O_3 nanorods

Abstract

We report radiation-induced lattice relaxation of the alpha -Fe_2O_3 and its associated alteration of particle morphology. The alpha -Fe_2O_3 was grown in solution by microwave hydrothermal synthesis technique in which more than half of the synthesized material was nanorods with axis along the (001) direction. Five sets of the synthesized alpha -Fe_2O_3 samples were irradiated using gamma-ray from ^{60}Co cell with doses of 600 kGy, 700 kGy, 800 kGy, 900 kGy, and 1 MGy. The investigation of the pristine and gamma-irradiated samples was carried out using X-ray powder diffraction, transmission electron microscope, and electron paramagnetic resonance methods. Results showed that continuous alternation of radiation-induced lattice compression and expansion causes lattice relaxation. The morphology of the alpha -Fe_2O_3 nanorods was found to change with absorbed dose into buckyball-shaped particles in response to the alternation of the compression and expansion strain. The EPR results showed a correlation between distortion in the O_h–FeO_6 octahedron structure and the relaxation of the lattice. The synthesis, growth, and relaxation are discussed in detail.