The Prepation And Optical Properties Of Rare Earth Ions Dysprosium And Cerium Doped Yttrium Aluminum Garnet Crystals

Yttrium aluminum garnet crystals(Y3Al5O12,YAG)have been widespread uses in solid state laser technology,illumination field and detection area,due to its high melting point,outstanding mechanical,chemical stability and excellent optical properties.The YAG,Ce:YAG,Dy:YAG and(Dy,Ce):YAG ceramic rods were prepared by solid-state reaction method sintered at different temperatures and then their single crystals were grown by an optical floating zone furnace using those ceramic rods sintered at 1450°C as raw materials,respectively.Then,these single crystals were subjected to anneal at high temperature.The microstructure and phases of the ceramics and the single crystals were characherized by XRD and SEM.The absorption spectra and the photoluminescence spectra of the YAG,Ce:YAG,Dy:YAG and(Dy,Ce):YAG single crystals were measured by a UV-VIS spectrophotometer and a PL spectrometer,respectively.The main experimental results are as follows:(1)The XRD results of the YAG ceramics sintered at different temperatures showed that the YAM phase(Y4Al2O9)was found in the ceramic sintered at 1000 °C.The YAG phase(Y3Al5O12)and the YAP phase(YA103)were found in the ceramic sintered at temperature higher than 1200 °C.As the sintering temperature increasing,the amount of the YAG phase in the ceramics increase,while the amount of the YAM and YAP phases in the ceramics decrease.The phases in the ceramic sintered at 1450? are main YAG phase.The lattice parameter of the YAG phase in the ceramics which sintered at various temperatures is between 11.952 A and 11.982 A which was calculated by its XRD diffraction peaks.The SEM images indicated that the grain size and the density of the YAG ceramic increase with the sintering temperature.(2)The XRD results of the Dy:YAG single crystals indicated that there is only a single YAG phase in the Dy:YAG single crystal.The maximum lattice parameter of Dy:YAG single crystals is 11.998 A,and is equivalent to that of YAG phase with a lattice parameter of 11.969 A.That is,the addition of Dy3+into the YAG did not cause severe distortion of the lattice structure.(3)The absorption spectra of Dy:YAG single crystals with different Dy concentration showed the transmittances of Dy:YAG single crystals in the wavelength range of 500?700 nm are higher than 80%,that is,the Dy:YAG single crystals with rather high transmittance in this wavelength range.There are several absorption peaks in the absorption spectra of Dy:YAG single crystals,and they are located at 325,352,366 and 447 nm.On increasing the Dy3+concentration,the transmittances of Dy:YAG single crystals at 325,352,366 and 447 nm decrease,while their absorption coefficients increase.The absorption coefficient of the annealed Dy:YAG crystal is higher than that of the as-grown Dy:YAG crystal due to the decrease of defect concentration during annealing.(4)When the Dy:YAG crystal was excited by a UV light with a wavelength of 352 nm,there are several emission bands in the photoluminescence spectrum of the Dy:YAG single crystal and they are located at 470?500 nm in the blue region,570?590 nm in yellow region and 660?685 nm in red region,which are corresponded to the transitions of Dy3+ions from 4F9/2 to 6H15/2,4F9/2 to 6H13/2 and 4F9/2 to 6H11/2,respectively.On increasing the Dy3+ concentration,the intensities of the emission peaks of the Dy:YAG crystal increase,and they reach their maximum values at 2at%Dy3+.However,the intensities of the emission peaks of the Dy:YAG crystal decrease as the Dy3+ concentration higher than 2at%.It has been found that the intensities of the emission peaks of the annealed Dy:YAG crystal is higher intensities of the emission peaks of the annealed Dy:YAG crystal is higher than that of the as-grown Dy:YAG crystal.(5)As the Ce:YAG and(Dy,Ce):YAG crystals were excited by a light with a wavelength of 465 nn,rather strong emission peak was found at 530nm in their photoluminescence spectra.The intensity of the emission peak of the annealed Ce:YAG and(Dy,Ce):YAG crystals is lower than that of the as-grown Ce:YAG and(Dy,Ce):YAG crystals.Moreover,the wavelength of the emission peak of the annealed Ce:YAG and(Dy,Ce):YAG crystals is shorter than that of the as-grown Ce:YAG and(Dy,Ce):YAG crystals.(6)Comparing the absorption spectrum of the annealed Ce:YAG crystal with that of the as-grown Ce:YAG crystal,it was found that the absorption coefficient at 255nm of the annealed Ce:YAG crystal is higher than that of the as-grown Ce:YAG crystal.However,the absorption coefficient at 465nm of the annealed Ce:YAG crystal is lower than that of the as-grown Ce:YAG crystal.(7)Comparing the absorption spectrum of the annealed(Dy,Ce):YAG crystal with that of the as-grown(Dy,Ce):YAG crystal,it was found that the absorption coefficient at 465nm of the annealed(Dy,Ce):YAG crystal is higher than that of the as-grown(Dy,Ce):YAG crystal.