Micro-defects and optical properties of YAG:Ce crystals prepared by optical floating zone method

The Y3Al5O12 (YAG):Ce ceramic rods and single crystals were prepared by solid state reaction and optical floating zone method, respectively. The XRD results showed that the phases in the YAG:Ce ceramics are mixture of YAG phase and YAlO3 (YAP) phase. There is only a single YAG phase in the single crystals of YAG:Ce. The mean positron lifetime of the YAG:Ce crystal decreases with increasing Ce content, and reaches minimum at 1 at.% Ce, then increases with Ce content. The mean positron lifetime of the YAG:Ce crystal is higher than that of YAG:Ce ceramic with the same chemical composition. The UV–visible absorption spectra of the YAG:Ce crystals indicated that the transmittances of the YAG:Ce crystals are higher than 90% in the wavelength range from 550 nm to 800 nm. The photoluminescence spectra of the YAG:Ce crystals showed wide luminescence emission peaks located in the range of 525–529 nm. A relatively high luminescence intensity is found in the YAG:Ce crystal with 1 at.% Ce. With further increase of Ce content, the luminescence decreases due to the fluorescence quenching effect.