High enhancement of green upconversion luminescence of Li+/Er3+/Yb3+ tri-doped CaMoO4

The polycrystalline Li+/Er3+/Yb3+ tri-doped CaMoO4 were prepared by complex citrate-gel method. Under excitation of 980 nm, Li+/Er3+/Yb3+ tri-doped CaMoO4 upconversion (UC) phosphors exhibited weak red (656 and 670 nm), blue (410 nm) and strong green UC emission peaks (530 and 550 nm), respectively. The measured green emission intensity of Li+ doped CaMoO4 was 83 times higher than that of Li+ non-doped CaMoO4 due to local crystal field distortion or break around Er3+ ions. The optimum doping concentration of Li+ ions was investigated. Moreover, the effects of Li+ concentration for UC emission intensity were studied in detail. (C) 2012 Elsevier B.V. All rights reserved.