Green up-conversion of C12A7-Ho3+ prepared by co-precipitation method

7CaO center dot 12Al(2)O(3) (C12A7) and Ho3+-doped 7CaO center dot 12Al(2)O(3) (C12A7-Ho3+) polycrystal powders were synthesized via co-precipitation followed by sintering at 1173 K. Crystal structures, thermodynamics characters and optical properties of crashed samples were examined by XRD, DSC/TG, FT-IR and Raman spectra analysis, respectively. Activation energy of crystallization for C12A7 polycrystals was calculated according to both Ozawa/Kissinger and modified Ozawa/Kissinger methods to be 813 or 791 ( for the former, only considering crystallization) and 1084 or 1077 kJ mol(1) (for the latter, taking both crystallization and nucleation into consideration) respectively. Growth morphology parameter (m) and crystallization mechanism index (n) of C12A7 were determined to be m = 3 and n = 4. Fluorescence effects of Raman spectra around 2000-2300 cm (1) and pure visible up-conversion emission centered at 540 nm were observed from C12A7-Ho3+ (1, 2 and 5 mol.%) powders under 488 nm laser diode and 808 nm Xe lamp excitation, respectively. Two mechanisms were proposed to explain up-conversion of pure green light process. (C) 2015 Elsevier B.V. All rights reserved.