科研之友
微信
新浪微博
Facebook
分享链接
摘要
Well-dispersed uniform spheres (approximate to 0.7-1.5 m in diameter) of YPO4 and (Y,Ln)PO4 (Ln = Eu, Tb, Dy, Ho, Tm, Ce, and Eu/Tb) tetragonal phosphate hydrates have been directly synthesized via microwave-assisted processing. The polycrystalline spheres, which are made of confined 10-17 nm nanocrystals, are direct solid solutions rather than a mechanical mixture of individual particles. Their growth follows an aggregation process, maintaining the composition of the material. The phosphate hydrates converted into anhydrous tetragonal materials via calcination, and the spherical shape and excellent dispersion of the original particles were well retained up to 1000 degrees C. Upon UV excitation, the YPO4:Ln(3+) samples exhibit characteristic emissions of Ln(3+) (Ln = Eu, Tb, Dy, Ho, Tm, and Ce) and yield red, green, near white, green, blue, and blue-green emissions, respectively. The color-tunable emissions (from green to red) can be varied by increasing the Eu content, and the Tb3+ Eu3+ energy transfer process was observed for the tetragonal phosphate in the Y/Tb/Eu system. The efficiency of the Tb3+ Eu3+ energy transfer was discovered to be approximate to 28% for (Y0.88Tb0.02Eu0.10)PO4. The thermal stability of (Y0.88Tb0.02Eu0.10)PO4 is lower than that of (Y0.98Tb0.02)PO4 and (Y0.95Eu0.95)PO4. Thus, the D-5(4) F-7(5) transition of Tb3+ at 546 nm splits into F-7(5) transition) were observed. (Y0.95Eu0.05)PO4/PVA transparent films were successfully fabricated by solution casting, and they exhibit both outstanding flexibility and high transmittances of 83% in the 400-850 nm region. The hybrid films can be coated on paper money for anti-fake labeling applications.
