Recombination processes and luminescence in Li6GdxY1−x(BO3)3-Eu crystals

Abstract

The results of investigation of thermally stimulated recombination processes and luminescence in Li6GdxY1−x(BO3)3-Eu crystals are presented. The steady-state luminescence spectra under X-ray excitation (XRL), the temperature dependence of steady-state luminescence intensity and the thermally stimulated luminescence curves (TSL) were measured at 90–500 K. In the steady-state X-ray luminescence spectra the band at 312 nm related to 6PJ→8S7/2 transitions in gadolinium ion and bands group at 580–700 nm associated with 5D0→7FJ transitions (J = 0…4) in Eu3+ ion were found to be dominant. The intensity of steady-state XRL of these bands in undoped crystal is increased by 15 times as the temperature changes from 100 to 400 K. The probable mechanisms of temperature dependence of steady-state luminescence intensity and their association with energy transfer of electronic excitations in these crystals are discussed. The investigations have shown the principle complex TSL peak with maximum at 150 K and a number of weaker peaks. The thermal activation parameters (activation energy, pre-exponential factor, kinetic order) for all intense TSL peak have been determined. The origin of small trapping centres caused TSL below room temperature and their association with defects in lithium cation sublattice is discussed.