Growth of Ce-doped Ba₃Gd(BO₃)₃ and Sr ₃Gd(BO₃)₃ single crystals by micro-pulling-down method and analysis of luminescence properties

Ce-doped double borates Ba₃Gd(BO₃)₃ and Sr₃Gd(BO₃)₃ (Ce:BGB and Ce:SGB, respectively) were grown by the micro-pulling-down method, and the luminescence properties of the crystals were investigated and compared with those of Ce-doped H-Ba ₃Y(BO₃)₃(Ce:H-BYB) crystals grown by the same method. Transmittance measurements showed the wavelength of absorption band was around 380 nm for all the samples. Emission bands corresponding to the 5d→4f transition of Ce³⁺ were observed at around 425 nm for Ce:BGB and Ce:SGB and at 435 nm for Ce:H-BYB. The photoluminescence decay times of Ce:BGB, Ce:SGB, and Ce:BYB were 29.5 ns, 35.2 ns, and 26.8 ns, respectively. The emission spectra obtained by excitation of ²⁴¹Am (an α-emitter) revealed that the host luminescence was dominant (at around 315 nm) in BGB and SGB and that a very low-intensity Ce³⁺ 5d→4f luminescence peak appeared at around 430 nm. The relative light yield strength observed under ²⁴¹Am excitation was corresponding to <100 and ∼270 photons/neutron for Ce:BGB and Ce:SGB, respectively, and these values were lower than that of Ce:H-BYB (∼400 photons/neutron).