Thermoluminescence studies on Cu-doped Li2B4O7 single crystals

Lithium tetraborate (Li2B4O7) is a tissue equivalent material and single crystals of this material doped with Cu are promising for dosimetric applications. In the present study highly transparent single crystals of lithium tetraborate (Li2B4O7) doped with Cu (0.5 wt%) have been grown using the Czochralski technique. The Li2B4O7:Cu crystals were studied using photoluminescence, X-ray diffraction (XRD), UV-vis transmission, time resolved fluorescence and thermoluminescence (TL) techniques. The TL readout of Li2B4O7:Cu crystals showed two well-defined glow peaks at 402 K (peak-1) and 513 K (peak-2) for a 4 K/s heating rate. While the low temperature TL peak-1 fades completely within 24 h at room temperatures, the main dosimetric peak-2 remains the same. The TL sensitivity of the grown single crystal is found to be 3.3 times that of a conventional TL phosphor, TLD-100. The Li2B4O7:Cu crystals showed a linear TL dose-response in the range from 1 mGy to 1 kGy. The TL analysis using a variable dose method revealed first order kinetics for both the peaks. Trap depth and frequency factor for peak-1 were found to be 0.81 eV and 5.2×109 s−1, whereas for peak-2 the values were 1.7 eV and 1.7×1016 s−1, respectively.