Optical and luminescence spectroscopy studies of electronic structure of Li6GdB3O9 single crystals

This article presents the study of electronic structure of Li6GdB3O9 single crystals and radiative relaxation of electronic excitations in them. The investigation was performed by the means of low-temperature optical and luminescence far-ultraviolet spectroscopy upon excitation by synchrotron radiation. On the basis of the low-temperature (T = 10 and 30 K) spectra of the reflection, recorded in the present research and the dispersions of the complex optical functions of εˆ(E),nˆ(E) and μ(E), calculated in the framework of the oscillator model, we have determined the parameters of the electronic structure of the Li6GdB3O9 crystals as follows. The value of the minimum energy for the interband transitions in the boron-oxygen framework is Eg=9.42eV, the energy position of the first excitonic peak in the excitation spectra for anionic excitons is En=1=7.46eV, the minimum threshold energy for excitation of excitons in linear chains of the Gd3+ cations is Ec=6.80eV. The excitation spectra of an intrinsic luminescence of Li6GdB3O9 crystals, recorded at 10 K in the range of the optical charge-transfer transitions O-Gd have a band with the maximum at ECT=6.57eV.