First-Principle Calculations And Preparation Of Spinel Zinc Ferrite

The band structure and the density of states of normal spinel zinc ferrite(Zn Fe2O4) has been investigated using first principles based on density functional theory. Calculation results illustrated that the normal spinel Zn Fe2O4 is direct gap semiconductor compound with a band gap of 0.9 e V. The axis of symmetry the spin density of states also indicates that spinel Zn Fe2O4 are not magnetic compound.The distribution patterns of Zn2+ and Fe3+ ions in the crystal structure of inverse spinel Zn Fe2O4, and electronic structure of different inverse constant spinel Zn Fe2O4 have been researched using first principle. Stability of structures that inverse constant is equal to 0, 0.25,0.5, 0.75 and 1 were analysed. The energy calculation of structure showed that the most stable cation distribution structure is R3 M, P1, CM for inverse constant of 0.25, 0.5, 0.75 and1, respectively. Magnetic analysis showed that partial inverse spinel is ferromagnetism with high saturation magnetization 7.5μB, 5μB, 2.5μB, respectively. The band structure of 0 and0.75 inverse spinel showed that they have the band gap with 0.9 e V and 0.037 e V,respectively. Electronic density of states showed that the electrons of the valence band top near the Fermi energy is mainly provided by the O 2p atomic orbitals electron, Zn 3d occupied the main position in the conduction band electron.Zinc ferrite crystals of inverse spinel structure is prepared via a molten salt route,Zn SO4?6H2O, Fe2(SO4)3?5H2O and Li Cl?H2O as raw material, molten salt, respectively. The crystal lattice constant analysed by XRD method is 8.421 ?. Particles are shown using scanning electron microscopy to be different sizes with good crystallinity, average grain scale up to tens of microns, and the size of large particle to be greater than 60 microns. The value of the saturation magnetization is 120 emu/g and the coercivity is 5.8(Oe) at 5 K. XPS analysis showed that the crystal only contain Fe3+ and Zn2+. M?ssbauer spectra analysis showed that Fe3+ distributed in the tetrahedral A sites and octahedral B1,B2 sites.With Li Cl?H2O as a flux, Zn SO4?6H2O and Fe2(SO4)3?5H2O as raw materials, Sn O2 as a dopant, zinc ferrite Sn-doped crystals were prepared. Crystal had good crystallinity, and themaximum grain size exceeded 70 microns as shown in SEM test. The value of the saturation magnetization is 130 emu/g and the coercivity is 1(Oe) at 5 K. XPS binding energy analysis showed the presence of ferric iron and Zn2+. M?ssbauer spectra of the zinc ferrite crystals analysis showed that Fe3+ distributed in the tetrahedral A site and octahedral B1,B2,B3 sites.Research on the effect of the ratio of raw materials on the proportion of Zn:Fe and magnetic properties showed that the proportion of Zn:Fe in the synthetic product increased gradually with the increasing of the ratio of raw materials, and the magnetism decreased gradually with the increasing of Zn content.