The role of defects in thermoluminescence of pure and rare-earth-doped magnesium tetraborate phosphor

The aim of this work was to elucidate the role of defects in energy storage and transfer in X-ray irradiated MgB4O7. Pure and terbium- and erbium-doped magnesium tetraborate was synthesized by the solid state reaction method. The band gap value Eg = 9 eV was estimated using the method of X-ray photoelectron spectroscopy (XPS). Absorption attributed to defects with energy levels located in the forbidden band was found from UV-vis spectroscopy. An interpretation of the thermoluminescence and radioluminescence spectra of pure and doped magnesium tetraborate was proposed. Two different mechanisms for enhancing the thermoluminescent response of MgB4O7 upon doping with rare earth elements were demonstrated.