Visible up-conversion luminescence in Er3+: BaTiO3 nanocrystals

Visible emissions at 548, 528 and 660 nm have been observed from the sol-ge l derived nanocrystalline Er3+:BaTiO3 powders under infrared excitations at both 980 and 810 nm. Combined with the energy level structure of Er3+ and the decay kinetics of the green emissions, the up-conversion mechanism has been analyzed and explained. The bright green emission at 548 nm has been a ttributed to the ground state-directed transition from S-4(3/2), which is p opulated through excited state absorption (ESA) for 810 nm excitation, and through both ESA and energy transfer (ET) processes for 980 nm excitation. (C) 2000 Published by Elsevier Science B.V. All rights reserved.