Li2B4O7:Mn for dosimetry applications: traps and mechanisms; pp. 279–295

Abstract

Thermoluminescence curves, kinetics, and Electron Paramagnetic Resonance (EPR) data were compared for Li2B4O7:Mn and Li2B4O7:Mn,Be radiation detectors. Analysis of the experimental data, both our own and published by other investigators, in connection with features of the crystal lattice structure allowed us to build models of traps and thermo­luminescence mechanisms. The thermoluminescence peaks used in dosimetry are connected with the release of holes trapped at bridging oxygen near Mn2+ (or Be2+), substituting for tetrahedrally coordinated B3+. The luminescence occurs at Mn2+ substituting for Li+. Two types of Mn2+ centres give different luminescence and EPR spectra. The effects of Mn2+ interaction with surrounding oxygen atoms are discussed both for the Mn2+ luminescence band and for the hyperfine structure of EPR. Kinetics measurements revealed an additional “hopping” barrier for a hole to get to a recombination centre after it has been released from a trap. A simple kinetics model is suggested to describe the experimental data. The studies of optical stimulation spectra and optically stimulated emptying of traps demonstrated the possibility of using Li2B4O7:Mn and Li2B4O7:Mn,Be radiation detectors with optically stimulated readout systems.