Studies Of Growth And Optical Properties Of Rare Earth Ions Doped Yttrium Aluminum Garnet Crystals

The Ce, Sm doped YAG ceramic rods were prepared by solid-state reaction method by using Y2O3, A12O3, Sm2O3 and CeO2 nano powder as raw materials. The influence of different sintering techniques on the density of the (Ce, Sm):YAG ceramic rod was studied. The single crystals of (Ce, Sm): YAG with different concentrations of Ce and Sm were grown by an optical floating zone furnace. The microstructures of (Ce, Sm):YAG crystals were characherized by XRD and SEM. The transmittance and absorption spectra of the (Ce, Sm):YAG crystals were measured by a UV spectrophotometer. The fluorescence spectra of the (Ce, Sm):YAG crystals were tested by a Photoluminescence Spectroscopy. The effects of different sintering techniques and the content of the dopants on the optical properties of the (Ce, Sm):YAG crystals were discussed. The main results are as follows:(1) A density higher than 95% of (Ce,Sm):YAG ceramic rods with with different content of dopants were sucessfully prepared by solid-state reaction method under 1450 ℃for 10 hours.(2) DSC and XRD results indicated that YAG is a compound formed by a reaction of Y2O3 and Al2O3. It has been shown that the YAM phase was formed at 1200℃, the YAP phase was formed at 1200℃, finally YAG phase was formed at 1450℃.The lattice structure of YAG did not changed after Ce and Sm doping.(3) In comparision with the YAM and YAP phases, the Ce:YAG with lat.%Ce powder sintered at 1450℃has relatively high fluorescence intensity.(4) The XRD paterns of the (Ce, Sm):YAG crystals grown by the optical floating zone method show very sharp diffraction peaks and narrow FWHM (Full width at half maximum), and these crystals are fully YAG phase. The crystals have high optical quality with homogeneous optical properties.(5) The transmittance and absorption spectra of the Ce:YAG crystals indicate that the transmittance of Ce:YAG crystals reach 90%—93% in the range of 500-800 nm. The absorption peaks located at 337.5 nm and 458 nm associated with the transition between 4f�'5d of Ce3+ ion. The absorption peak intensity and the absorption coefficient of Ce:YAG increase with the Ce content, and reach their maximum values at 2 at.% Ce. However, they decrease at 5 at.% Ce. This may be due to the solid solubility of Ce3+ in YAG is 2 at.%.(6) The fluorescence spectra of the Ce:YAG crystals with different Ce contents show wide fluorescence emission peaks located in the range of 525-529 nm. A relatively high fluorescence intensity is found in the Ce:YAG crystal with 1 at.% Ce. With further increase of Ce3+ content, the fluorescence intensity decreases due to the fluorescence quenching effect. meanwhile Ce:YAG fluorescence peaks redshift due to the disorder of the crystal.(7) The fluorescence peaks of Sm:YAG crystal grown by optical floating zone method were mainly distributed in 568 nm,618 nm and 652 nm associated with the transitions between 4G5/2�'6H5/2、4G5/2�'6H7/2、 4G5/2�'6H9/2 of Sm3+ ions, respectively. And the peak of 618 nm is relatively high.(8) The fluorescence spectra of (Sm, Ce):YAG crystals with different content of Sm and Ce present wide emission peaks of Ce:YAG located in the range of 524 nm-530 nm. And the red light emission peaks appear at 568 nm, 573 nm and 619 nm due to the energy transfer between Ce3+ and Sm3+. The 568 nm and 573 nm emission peaks associated with the transitions between 4G5/2-6H5/2 of Sm3+ ion, the 619 nm peak associated with the transitions between 4G5/2-6H7/2.The red light emission peaks increase with the Sm3+ content.