Structural and spectroscopic properties of Yb3+-doped MgAl2O4 nanocrystalline spinel
Magnesium spinel (MgAl2O4) powders doped with Yb3+ ions have been synthesized by a sol–gel method and heat-treated in the range of 700–1000 °C for 3 h. XRD patterns indicated that the powders have a cubic structure with high crystallite dispersion. Nanoparticles in the range of 10–30 nm are obtained as a function of the dopant concentration and sintering temperature. The main Yb3+ zero-phonon line is located at 976 nm. The spectroscopic properties of the Yb3+ ions are characterized by broad absorption spectroscopy and emission spectroscopy. Even at low temperature, the spectra reveal a strong distorted spinel lattice due to the high inversion rate between Mg2+ tetrahedral sites and Al3+ octahedral sites. The substitution of Mg2+ ions by Yb3+ ions favors the creation of Yb3+ ion pairs which are observed in the cooperative luminescence spectra at around 500 nm. The luminescence decays are influenced by both the Yb3+ content, the energy transfer between ions and by the presence of pairs and aggregates. Detailed analysis of the observed structural and spectroscopic measurements has been described in this manuscript.