We have investigated Li4SiO4 scintillation crystals for their possible application in neutron detection due to high Li content and low density of 2.35 g/cm3. The micro-pulling-down method employing the Ir crucible and afterheater was optimized for crystal growth of Li4SiO4 taking into account the Li evaporation. To grow high-quality crack-free single crystals, the heating power was increased to establish milder temperature gradient, thicker meniscus, smaller crystal diameter and resulting smaller stress in the as-grown crystals. The undoped, Ti-, Cr-, and Al- doped crystals were prepared and studied. Radioluminescence measurements under X-ray excitation showed quite high overall scintillation efficiency of the Ti-doped sample reaching as high as 250% of that of Bi4Ge3O12 reference scintillator. The emission spectrum was dominated by one broad band peaking at 350 nm related to Ti4+ impurity. Reasonable light yield of 10000 photons/neutron was found. However, its long decay time of 54 μs might be a limitation especially for high counting rate applications. The overall scintillation efficiency of the Cr3+ sample was much lower and the spectrum shows one broad peak at 463 nm which does not correspond to Cr3+ luminescence. The radioluminescence spectrum of the Al-doped sample resembled to that of the Ti-doped one, just its magnitude is considerably lower, which was explained by Ti contamination. Peculiarities and optimization of crystal growth and a preliminary sketch of luminescence mechanisms and dopant incorporation are discussed.
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