Preparation and upconversion luminescence of Er3+/Yb3+ codoped Y2Ti2O7 nanocrystals

Er3+/Yb3+ codoped pyrochlore-type (Y0.99-xEr0.01Ybx)(2)Ti2O7 (x = 0, 2.5, 5.0, 7.5, 10.0 and 12.5 mol%) nanocrystals have been successfully prepared by the sol-gel process with citric acid as chelator. The samples annealed at 800 degrees C for 1 h exhibit good crystallinity and narrow size distribution with average size of 20-30 nm. Upon 980 nm excitation at room temperature, green (at similar to 525 and 545 nm) and red (at similar to 660 nm) upconversion emissions were observed, which are ascribed to the (H-2(11/2), S-4(3/2)) -> I-4(15/2) and F-4(9/2) -> I-4(15/2) transitions, respectively. And also, it has been found that the annealing temperatures and the Yb3+ ion doping concentrations have greatly influenced on the upconversion luminescence intensity. The results show that Y2Ti2O7 is an excellent host material for efficient upconversion nanophosphors. (c) 2011 Elsevier B.V. All rights reserved.