Stokes and anti-Stokes luminescence from Eu/Yb:BaB4O7 nanocrystals

The spectroscopic and structural properties of surface crystallized Eu3+ ions and Yb3+ ions co-doped oxyfluoroborate glass ceramics have been studied. Luminescence measurements reveal higher cross-sections in the ceramic, on excitation with 464 nm and 976 nm laser radiations. Studies with polarized light as well as SEM images confirm crystallization in the ceramic and the XRD studies show that α-BaB4O7 crystals are formed on the surface after annealing. These structural changes significantly alter the luminescence characteristics of Eu3+ and Yb3+ ions. A bright red emission from Eu3+ ions is observed under 976 nm excitation. The photophysics involved in this emission has been explained.