Recent advances in rare earth scintillation crystals

Rare earth scintillation crystals act as an important media of radiation detection that could convert high-energy rays or high-energy particles to ultraviolet/visible fluorescence pulse. From the perspective of the periodic table, the rare earth scintillation crystals can be divided into rare earth halide and rare earth oxide compounds. In this review, we summarize the basic scintillation properties and crystallographic structure characteristics of some typical rare earth scintillation crystals. Rare earth ions exhibit excellent luminescent properties due to their unique 4 f electronic structure. Among the lanthanide ions, Ce3+, Pr3+, Eu2+ are chosen as efficient activator ions since they usually show spin- and parity-allowed 5 d ® 4 f transitions. The 4 f orbits of rare earth ions are shielded by filled 5 s and 5 p shells, while 5 d orbits are strongly affected by the surrounding without any shielding effect. The scintillation properties are therefore determined by the composition and structure of rare earth scintillation crystals. On the other hand, some rare earth ions, such as Y3+, La3+and Lu3+, are optically inactive, which can be regard as the ideal chemical compositions of matrix materials. An insight into the rare earth scintillation crystals is provided from the view of composition design and bulk crystal growth. We also discuss the patent protection of rare earth scintillation crystals in China. Future prospects of rare earth scintillation crystals have been briefly mentioned.