The diffusion study of oxygen atoms in Co x/3 Ni (5− x)/3 Sb 1/3Fe 1O 4 ferrite

Abstract

The oxygen diffusion in polycrystalline samples Co x/3 Ni (5− x)/3 Sb 1/3Fe 1O 4 ( x=0, 1, 2, 3, 4) at an annealing temperature of 823 K for 1 min, was studied. The diffusion coefficient was calculated using the equation D=( σKT/ Ne 2) t. It was found that the oxygen diffusion is characterized by a relatively small activation energy (0.54 eV) and low pre-exponential factors D 0≈10 −13 –10 −14 cm 2 s −1 . These results suggest the oxygen diffusion in ferrite under consideration occurs by means of structural vacancies with their concentration about 10 −11–10 −13. The substitution of Co 2+ ions decreases the diffusion coefficient up to x=1 and then increase it. The X-ray analysis showed that the spinel phase was completely formed at 12 h sintered at 1473 K. From the correlation between ionic radius and radius of octahedral and tetrahedral sites, the theoretical lattice parameters were calculated and a suggestion of cation distribution for the given ferrites was determined.