Preparation And Luminescent Properties Of Al₂O₃ Doped With Rare Earth Elements

Because of the excellent physical and optical properties, Al₂O₃ ceramic powder doped with rare earth and transition metal elements was widely used in the radiation dose detection, fluorescence tracking monitoring and other fields. In this paper,Al₂O₃:Eu, Al₂O₃:Eu:Tb and Al₂O₃:Cr luminescent ceramic materials were prepared by the chemical combustion synthesis technique. The samples were characterized by scanning electron microscope（SEM）, X-ray photoelectron spectroscopy（XPS）, X-Ray Diffraction（XRD） and photoluminescence spectroscopy. The optimum concentration and annealing temperature of samples were ascertained by investigating for the doping concentration and annealing temperature effect on the samples photoluminescence properties.Al₂O₃:Eu ceramic powder was prepared by the raw materials of Al（NO3）3·9H2O and Eu（NO3）3·6H2O. The XPS results showed that the Eu ions existed in two valence states, namely the Eu3+, Eu2+ ions. The morphology of the sample annealed before and after was micron flake. The X-Ray Diffraction（XRD） analysis showed that the crystallinity of the powders increased with the elevated annealing temperature, the best doping concentration of crystallization is 0.055% mol. The photoluminescence（PL） measurements of Al₂O₃:Eu ceramic powder induced by excitation wavelength of398 nm exhibited two well defined peaks of the Eu3+ at 592 nm and 618 nm. The main luminescence peak position didn’t changed with the increase of annealing temperature.The luminescence intensity of the main peak first increased then decreased with the elevated annealing temperature and the impurity concentration. The optimum annealing tempertature was 900℃ and the optimum concentration was 0.055 mol%.Al₂O₃:Eu:Tb ceramic powder was prepared by the raw materials of Al（NO3）3·9H2O, Eu（NO3）3·6H2O and Tb（NO3）3·6H2O. Because there existed Eu3+,Tb3+, Eu2+ three kinds of rare earth ions in the samples, the experiment results showed the red, green, blue three colored light. The photoluminescence spectra ofAl₂O₃:Eu:Tb ceramic powder were measured at a definite Eu3+ ions concentration（0.04mol%） and various Tb3+ concentrations and heat-treated temperature at800℃.The results showed the photoluminescence peak intensity of Eu3+ at 592 nm,618nm, 653 nm and 705 nm increased with the increasing of Tb3+ ion concentration.However, the photoluminescence peak intensity of Tb3+ at 545 nm deceased with the increasing of Tb3+ ion concentration from 0.14mol% to 0.17mol%.Al₂O₃:Cr ceramic powder was prepared by the raw materials of Al（NO3）3·9H2O and Cr（NO3）3·9H2O. The sample was small slice. There were two wide bands at426 nm and 570 nm in excitation spectrum under an emission wavelength of 694 nm,which correspond to the transition of Cr3+ 4A2（4F） â†' 4T1（4P） and 4A2（4F） â†' 4T2（4F）,respectively. The transition of Cr3+ 2E â†' 4A2 occurred at 694 nm in emission spectrum and the optimum doping concentration of Cr3+ ion was 0.02mol%.