Luminescence processes in Ti-doped LiAlO₂ single crystals for neutron scintillators

LiAlO₂ can be considered as a good candidate for neutron scintillator host matrix due to the high Li content and high energy deposit of reaction of ⁶Li isotope with neutron. Low density (2.75 g/cm³) is of advantage to achieve low sensitivity of background gamma radiation in mixed radiation fields. Ti-doped LiAlO₂ shows relatively high neutron light yield comparable to that of the Li-glass standard neutron scintillator. At room temperature the Ti⁴⁺ charge transfer (CT) luminescence at 375 nm with the 2.5 µs decay time is the leading emission process. Besides the CT luminescence host emission at shorter wavelengths (350 nm), defect-related emission at 440 nm and impurity Fe³⁺ luminescence at 740 nm are observed. Their emission spectra, excitation spectra and decay kinetics including temperature dependences were studied. Luminescence mechanism in the material and interplay between the luminescence processes are discussed together with possible role of nonstoichiometry and Mg codoping.