Redshift of the optical gap in ferrite doped Gd₂O₃

We report the measurement of the optical bandgap in ferrite doped Gd2O3. Doping of the nickel zinc ferrite (Ni0.5Zn0.5Fe2O4) nanoparticles to Gd2O3 powder was done through thermal decomposition of the mixture at 1000 °C. The average grain size of the thermally decomposed mixture was determined to be around 95 nm and contained phases of cubic Gd2O3, GdO, and orthorhombic prisms of GdFeO3. The imaginary part of the complex dielectric function was calculated from the absorbance measurements that showed an optical bandgap at 1.8 eV. The observed value of the fundamental energy gap is on average 4.0 eV smaller than suggested by early experiments. A model for the ferrite doped Gd2O3 was constructed to suggest that the Ni, Zn, and Fe atoms occupy Gd sites in the Gd2O3 lattice. A new band at Γ point is formed due to the hybridization of the atomic orbitals of dopant and Gd3+ that shifts the fundamental absorption edge to the red part of the photon energy spectrum. Despite having a high density of negatively charged carriers contributed by the dopant, the onset of the direct interband transitions is clearly resolved.