Annealing effect on the luminescence properties of BaZrO3:Yb3+ microcrystals

Yb-doped barium zirconate (BaZrO3:Yb3+) was synthesized by a hydrothermal method at 100 degrees C. It presents a cubic perovskite crystalline phase, which is stable between 100 and 100 degrees C. Upon increasing the annealing temperature, two major changes are observed. (1) The near infrared (NIR) absorption band of Yb3+ decreases, and an enhancement in both the NIR emission of Yb3+ single ion and visible emission of Yb3+ pairs occurs, which is attributed to the reduction in impurities. (2) The annealing process induces new absorption bands in the ultraviolet-visible (UV-vis) region that increase as annealing temperature increases. These results suggest that reduction in Yb3+ to Yb2+ is taking place. The visible emission is considered to be a cooperative emission from Yb3+ pairs. Under UV and visible excitation, no emission of Yb2+ ions was observed. This suggests that the broadband absorption in the UV-vis region might be related to F color centers, which are responsible for the inhibition of the Yb2+ ion emission. (C) 2008 American Institute of Physics.