Relationship between infrared radiation and crystal structure in Fe-Mn-Co-Cu-O spinels

Ni3+ and Cr3+ doped Fe-Mn-Co-Cu-O spinels have been prepared by solid phase sintering. The valence states and distribution of transition ions in the spinel crystals are inferred by the consideration of thermodynamic principle and crystalline field theory. The microstructure and performance of those are studied by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and IRE-2 infrared radiant instrument. Ni3+ and Cr3+ occupy the vacancies or substitute the other ions in the spinel structures and form diverse spinel structures, which exhibit infrared integral emissivities of 0.93 in the whole band, and 0.94 in the band within 14-25 μm too. The content of Fe2O3 and MnO2 in the spinel crystals changes, maybe it induces infrared radiativity of spinels differently.