Thermal neutron scintillation improvement in Ce:Li6Y(BO3)3 single crystals by thermal treatment

The development of efficient, low-cost, and stable solid-state materials for portable thermal neutron detection is highly expected in order to substitute the currently used He-3 and BF3 tank detectors. A few Li-based glasses and halide compounds have emerged as candidates, however, all of them present critical drawbacks for their practical implementations. Ce:Li6Y(BO3)(3) is a priori a very promising oxide candidate that however has been disregarded so far due to its negligibly low light yield, caused by a poor crystalline and optical quality. In this study, we demonstrate that a post-growth thermal treatment is the key parameter to drastically reduce the concentration of intrinsic defects and scattering centers that lead to severe non-radiative recombination of excited electrons. Even though this annealing step also involves the oxidation of activator Ce3+ ions to Ce4+, a drastic enhancement of the light yield by similar to 600% is achieved independently of the Ce3+ concentration within the considered range. The obtained light yield of 4650 ph n(-1) is already close to that of reference Li-glass (commercial GS20 with 6000 ph n(-1)). An additional improvement can be envisaged upon further optimization of the Ce3+ concentration and the annealing time, so that Ce:Li6Y(BO3)(3) reaches a light yield comparable to the state-of-the-art one for thermal neutron detection.

Automated summary

This study demonstrates that a post-growth thermal treatment is crucial for enhancing the light yield of Ce:Li6Y(BO3)(3) oxide. By reducing the concentration of intrinsic defects and scattering centers, the light yield is significantly improved by approximately 600%. Further optimization of the Ce3+ concentration and annealing time can potentially achieve a light yield comparable to state-of-the-art materials for thermal neutron detection.