Crystal growth, structure, optical and scintillation properties of Ce3+-doped Tb2.2Lu0.8Al5O12 single crystals

Abstract

Single crystals of undoped and 0.5 at.% Ce³⁺-doped Tb_2.2Lu_0.8Al₅O₁₂ (LuTbAG) with dimensions of up to ∅25 × 30 mm³ have been successfully grown by the Czochralski pulling method. After the single-phase was confirmed using X-ray diffraction analysis, the absorption coefficient of the undoped LuTbAG was investigated. By using the results of Rietveld refinement and electron probe micro-analysis, the site occupations in undoped and Ce-doped LuTbAG crystals were indirectly revealed. The optical and scintillation characteristics of Ce³⁺-doped LuTbAG crystals were investigated in detail. In the transmittance spectra, Ce³⁺-doped crystals showed not only absorption bands at around 340 and 459 nm which are ascribed to the transition from the 4f ground state to the 5d excited state of Ce³⁺, but also the typical 4f–4f absorption of Tb³⁺. Under X-ray and UV excitation, strong emission peaks at 530 nm and 565 nm because of the Ce³⁺ 5d–4f transition and the line emission traces of 4f–4f transitions featuring Tb³⁺ were both observed for the Ce³⁺ doped crystal. The scintillation efficiency of the LuTbAG:Ce crystal under X-ray excitation was about two times larger than that of a BGO commercial crystal measured under the same conditions. Pulsed X-ray luminescence measurements showed two exponential decay components of 1.8 μs and 161 μs. These initial results make the LuTbAG:Ce crystal an attractive and promising scintillator for X-ray detection. In addition, the point defects in the undoped and Ce-doped LuTbAG crystals were investigated by a wavelength-resolved thermoluminescence technique.