Voloshyna O. Obtaining and characteristics of compounds REAO4 (RE - rare earth element, А - V, Nb, Ta) for scintillation applications

This thesis is devoted to study of luminescence and scintillation characteristics of materials based on compounds with the common formulae REAO4 (RE - rare earth element, А - V, Nb, Ta). Yttrium and gadolinium tantaloniobates in the full concentration range of Nb5+/Ta5+ substitution were obtained with solid-state synthesis without the high-temperature solvent. The effect of the cation substitution in the tantalate matrix on the luminescence and scintillation characteristics was studied for mixed crystals RENbxTa1-xO4 (RE=Y or Gd, х=0 - 1). In particular, it was shown that with substitution of the tantalum with niobium in the matrix the enhancement of the light yield was observed - linear for gadolinium and non-linear for yttrium tantaloniobates. Single crystals of the yttrium and gadolinium vanadate were grown by the Czochralski technique. The light yield, energy resolution at 662 keV and decay time of luminescence was determined as 6300 ph./МeV, 16,1 %, 15 mks for YVO4, and 12000 ph./МeV, 15,7 %, 13 mks for GdVO4 , respectively. Studied crystals demonstrated slower luminescence and the relative light yield of 59,7 % and 99,8 % for YVO4 and GdVO4, respectively, compared to the single crystalline sample of GSO:Ce (Gd2SiO5:Ce). Gadolinium vanadate was proposed as a scintillation material for the first time. Single crystal of gadolinium tantaloniobate with the light yield of 1400 ph./MeV (700 % relatively to the light yield of PWO (PbWO4)) and the main luminescence decay time component of 17 ns (similar to the PWO decay time with ?= 10 ns) was grown by the Czochralski technique for the first time. The achieved scintillation parameters in the rare-earth tantaloniobates allow one to consider them as promising dense scintillators for high-energy particles registration.