Impact of crystallization method on the strain, defect formation, and thermoluminescence of YAG:Ce crystals

Abstract

Numerous studies have addressed the excellent properties of Ce-doped Y3Al5O12 garnet (YAG) crystals for utilization in lighting applications. However, the differences in the photoluminescence and defect formation of YAG crystals obtained by different methods have not been elucidated. In this study, the effects of the crystallization path of YAG:Ce on the local structure of its emission site and defect formation were investigated. Ce-doped YAG crystals were prepared in three ways: (1) solid-state reaction, (2) heat-treatment of YAG glass, and (3) crystallization from a supercooled YAG melt by a controlled cooling process from a deep supercooled state. For the sample obtained by the crystallization of a supercooled melt, the photoluminescence peak red-shifted by 3 nm relative to those of the other samples, and the thermoluminescence increased by a factor of 50–5000. As the thermoluminescence intensity has been associated with the defects formed, positron annihilation lifetime spectroscopy was performed to investigate the defects. The positron lifetimes of all crystallized samples exhibited two components, and the crystallized sample obtained by melt-cooling showed the longest lifetime among the samples.