Tuning the local structure of (Sm, Co) Co-doped Al2O3 system for optical band gap and low dielectric loss

This study is about the qualitative description of the high dielectric constant (>10³) and low dielectric loss in a two co-existing phases. According to earlier beliefs, a material with high dielectric constant will exhibit high dielectric loss. However, this study gives the opposite, where a material with high dielectric constant can exhibit low loss. Herein, we report on the effect of tetrahedral – octahedral interaction in a γ- Al₂O₃ and CoAl₂O₄ biphasic system. Phase identification was carried out using Synchrotron x-ray carrying a wavelength of 0.7 Å. The disorder caused by varying cobalt (Co) concentration results in a two co-existing phase system with varying local polarizability due to mixing of cations in a host matrix. In addition, a decreasing trend in the band gap energy has been observed for both the phases as a function of increasing Co concentration, which is attributed to the intra-gap localized density of states determined from the UV–Vis diffuse reflectance spectroscopy (DRS).