Crystal growth and optical properties of new neutron detectors Ce/sup 3+/:Li/sub 6/Gd(Y)(BO/sub 3/)/sub 3/

An efficient new scintillator that contains lithium, gadolinium and boron, all three of which possess large neutron capture cross section isotopes for highly exothermic reactions has been recently developed. The homologous yttrium material was also investigated. These compounds of composition Li/sub 6/Gd(Y)(BO/sub 3/)/sub 3/ can be activated by Ce/sup 3+/. The synthesis of powders was carried out by high temperature solid state reaction from the starting materials LiOH, H/sub 2/O, H/sub 3/BO/sub 3/, Gd/sub 2/O/sub 3/ or Y/sub 2/O/sub 3/ and Ce(NO/sub 3/)/sub 3/, 6H/sub 2/O of purity ?99.99%, under a flow of Argon/H/sub 2/ (5%). Under UV excitation they show a broadband emission peaking at 390 nm. The gadolinium emission lies near the maximum of a 4 f-5 d Ce/sup 3+/ absorption band, so efficient Gd/sup 3+/-Ce/sup 3+/ transfer occurs. Ce/sub 3+/:Li/sub 6/Gd(Y)(BO/sub 3/)/sub 3/ crystals were grown by the Czochralski method in a resistance heating furnace using a conical vitreous carbon crucible of 150 cm/sup 3/ under deoxygenated pure argon. Monocrystalline boules as large as 3 cm diameter, 6 cm length have been obtained. The interest of these new materials is the high scintillation efficiency-as much as six times that of Li-glass scintillators for the Gd material. Moreover these scintillators offer the ability to tailor their response to the neutron spectrum by varying the isotopic composition of the key constituents (lithium, gadolinium (yttrium), boron).