Sidletskiy O. Scientific and technical basics of obtaining oxide scintillation crystals based on substitutional solid solutions

The work is devoted to the development of science and technical basics of targeted obtaining of high efficient inorganic scintillation crystals based on substitutional solid solutions. Structure, luminescent, and scintillation properties of the obtained crystals have been studied. The presence of spatial inhomogeneities of 1-3 µm size in Lu2-xGdxSiO5:Ce has been shown due to fluctuations of Lu3+ і Gd3+ content in crystals, as well as nanosize inhomogeneities in the form of planes and columns formed at selective substitution of Lu3+/Gd3+ ions in LGSO:Ce, and Al3+/Ga3+ ions in YAGG:Ce in corresponding crystallographic sites were illustrated. The concentration ranges, optimal rate (0.5 - 2 mm/hour), thermal conditions of large-size oxide crystal growth by the Czochralski method has been determined: Y3Al5-xGaxO12:Ce (0<x<5) with the diameter of up to 35 mm and the length of up to 150 mm; YAl1-xGaxO3:Ce (0<x<0.1) with the diameter of up to 25 mm and the length of up to 100 mm. The compositions, optimal rate (3-60 mm/hour), thermal conditions of oxide crystalline fiber growth by the micro-pulling down (µ-PD) method have been determined: Lu2-xGdxSiO5:Ce (0<x<1.6) with the cross-section of up to 2х2 mm and the length of up to 100 mm; Y3Al5-xGaxO12:Ce (3<x<5) with the diameter of up to 2 mm and the length of up to 70 mm. The common phenomenological approach to targeted obtaining of oxide sciтtillation crystals with improved light yield has been formulated, in particular, the tendency has been noted to the increase of light yield of solid solutions at substitution of atoms with the ionic radii ratio RА/RВ in the 1.07-1.15 range, the difference in bandgaps of solid solution components deltaEg>0.2 eV, the difference of electronegativities of substituted atoms 0.3-0.6. Keywords: functional materials, scintillators, solid solutions, oxide crystals, light yield, structure properties, optical properties.