Synthesis and Characterization of Indium Oxide Doped Hematite xIn₂O₃·(1-x)α-Fe₂O₃ Solid Solution

Abstract

Indium oxide-doped hematite xIn 2 O 3 ·(1-x)α-Fe 2 O 3 (x= 0.1-0.7) solid solution systems were synthesized using mechanochemical activation. The microstructures, magnetic and thermal properties of the system were dependent on In 2 O 3 molar concentration x and ball milling time. XRD results showed that the completion of In 3+ substitution of Fe 3+ in hematite lattice occurs after 12 h ball milling for x = 0.1. For x = 0.3, 0.5 and 0.7, the substitutions between In 3+ and Fe 3+ into hematite and In 2 O 3 lattices occur simultaneously. The lattice parameters of hematite and In 2 O 3 vary as a function of ball milling time. The change in these parameters was due to ions substitution between In 3+ and Fe 3+ and the decrease in grain sizes. Mössbauer spectra of the system with x = 0.3 were fitted with three sextets and two quadrupole-split doublets after milling, representing In 3+ substitution of Fe 3+ in hematite lattice and Fe 3+ substitution of In 3+ in two different sites of In 2 O 3 lattice. TGA results showed that the hematite decomposition is enhanced due to the smaller hematite grain size. The crystallization of hematite and In 2 O 3 was suppressed with the drops of enthalpy values due to the stronger solid-solid interactions after ball milling. These caused gradual In 3+ -Fe 3+ substitution in hematite/In 2 O 3 lattices.