Preparation And X-ray Storage Properties Of Eu³⁺ Doped CaGdAlO₄ Phosphor With Red Light Emission

Computed Radiography?CR?is widely used in many fields such as medical,non-destructive testing and security screening.The key part of its imaging is the phosphor on the imaging board.At present,commercial X-ray phosphors has the disadvantages of poor stability,easy decomposition of harmful gases,pollution of the environment,etc.Attention has been paid to rare earth doped oxide-based X-ray phosphors.Such as the yttrium aluminate?CaGdAlO₄,CGA?laser crystal is a good candidate matrix material,because the oxide group has good X-ray irradiance.The detector for receiving optical signals during medical imaging is mainly a Charge Coupled Device?CCD?.The peak response of the CCD is mainly in red and near-infrared light.Therefore,in order to enhance the signal coupling efficiency,it is necessary to develop a red light emitting oxide storage phosphor.In this paper,Eu³⁺-doped yttrium aluminate phosphor material(CaGd_1-xAlO₄:xEu³⁺(CGA:xEu³⁺)with red light emission was prepared by self-propagating combustion method.The relationship between photoluminescence and photo-stimulable luminescence and doping concentration of CGA:Eu³⁺was studied by means of XRD,excitation,emission spectroscopy,scanning electron microscopy,thermoluminescence spectroscopy,afterglow attenuation and photo-stimulable response curves.It was found:1.X-ray storage phosphor of CaGdAlO4:xEu³⁺synthesized by combustion method,mainly with red light emission at 620nm.The emission and excitation spectra indicate the presence of high concentration quenching because of the energy transfer from Eu³⁺to Gd³⁺.When the Eu³⁺doping concentration is 0.003,the afterglow decay time is 5 min,and the light excitation intensity is the largest,which can be used as the optimal concentration for storage performance optimization.2.The CGA:0.003Eu³⁺sample was subjected to a reducing atmosphere?vacuum,nitrogen and carbon embedding?,heat treatment at 800?for 3 hours,and it was subjected to excitation luminescence characterization.The photo-stimulable luminescence shows that the sample's optical storage performance has been improved,proving that the reducing atmosphere can cause a deep trap that is related to the oxygen vacancy.3.By changing the annealing temperature of the reducing atmosphere,the best sample was obtained when the CGA:0.003Eu³⁺sample was subjected to a nitrogen atmosphere and heat treatment at 1300?for 3 h.It can be seen from the emission spectrum and the Fourier transform infrared spectrum that its luminescence is significantly enhanced,which is related to the reduction of OH-in the sample;Afterglow,photo-stimulable and pyrolysis curves show that the intensity of the afterglow has hardly changed,and the photo-stimulable luminescence t has been significantly enhanced.Because there are two kinds of traps in the sample,the high temperature reducing atmosphere makes the number of shallow traps in the sample unchanged,and the number of deep traps increases.4.Explained its storage mechanism.5.The X-ray luminescence curve shows that with the increase of X-ray irradiation time,the absorption capacity shows a trend of linear increase?in the range of 0-11.8Gy?.When the X-ray absorbed dose is 1.2Gy,higher quality X-ray imaging is obtained.The above experimental results indicate that europium-doped CGA X-ray phosphor materials have potential application prospects in computer X-ray medical imaging technology,and are oriented towards CCDs as photodetectors.